Should I use long interconnects, or long speaker cables?

Currently, my equipment rack is placed centered between and behind the speakers.  I’m getting acoustic feedback (rumble) from my tt due to it’s location.  Successfully, I have eliminated this rumble by using a KAB rumble filter.  However, this seems to me like a bandaid approach, and I would like to try to eliminate the use of this filter if possible.  I’m thinking of moving my equipment rack to the side wall to try to eliminate the rumble filter.  My question is, there are two ways to do this.  Is it best to:
#1). Move everything (including the amplifier) to the side wall, and use long speaker cables to connect the amplifier to the speakers.  
#2. Move everything, except leave the amplifier on the floor (on a separate amp stand), and run a long interconnect (20’-25’) from the preamp to the power amp (my preamplifier is single ended only)?
In advance, thanks for your guidance!
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I appreciate your suggestions.  I’ve already tried the spring route, and that was no help (however, I used the springs under my two subs, and what a nice improvement I received).  I believe that the feedback is acoustic in nature (not being mechanically transmitted through my wall mount shelf).  My problem (I think) is due to the fact that the tt is mounted almost directly under the location where my coffered ceiling is meeting the back wall.  There is so much bass energy in that location.
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NO !
Unbalanced Interconnects longer than 1.5m may rouin sound.
If you can use balanced lines (XLR) you can go up to 150m, no problem.
Speaker cables should be as short as possible. Length can be compensated by cross section. The ratio is linear: length grow by 2, so should grow the cross section.
The best is to use monoblocks, placed close to the speakers, with extra short cables and run as much as you need between the pre and powers with balanced XLR cables.

Long speaker cable is best if your not running balanced as with single ended you will loose sound quality.
Its not acoustic feedback. Unless maybe you have the flimsiest turntable ever made and it has a dust cover and you leave the dust cover on- and even then I seriously doubt it. What you have is mechanical vibrations coming from the floor and rack right into the turntable. Springs under the subs helped, but it wasn't the subs. They helped by reducing the vibration energy the subs were putting into the floor, from where it travels up into the turntable. 

What you want are springs under the turntable. Its very important with springs that they be matched to the mass of the component. Generally speaking you want a spring that will be compressed at least half way under load. If your turntable compresses the springs half way or more give them a try. Also check to see how it bounces on the springs. If it bounces fast the springs are too stiff. What you want is nice and slow, 2Hz at most. 

The cheapest/easiest springs to try first are Nobsound from Amazon. With these you can remove springs to adjust for load. They come with 7 per unit and you will probably need only 3. My table is 75 lbs and I only use 4 springs each to do four corners. At under $35 including shipping these are an amazing deal and should definitely be tried. They WILL fix your problem. 

The Nobsound spring test will prove I'm right, and you will be able to use them under speakers and other components as well. Then once you know just how good this works the next step are Townshend Pods, which take spring engineering to another level. Pods use a bellows and air valve for perfect damping to allow micro vibrations to be completely absorbed while controlling larger amplitude movement. I recommend Nobsound because they are cheap and well worth trying. I recommend Townshend because if you can afford them they are much more refined and well worth the extra investment.

I am using long balanced interconnects (3M) and very short speaker cables to my mono blocks. This arrangement has proven to me to be the best in sound quality.

+1 on Balanced interconnect/short speaker cables, @ozzy .

Rumble from a turntable is most likely due to poor isolation. Either the turntable itself, or equipment being influenced by vibrations.
Also, improperly set up subs can accentuate rumble.
It's hard to pinpoint without knowing what is in your system, how you are placing equipment, as well as how your room is set up.
You can post images in Virtual Systems. It would help alot.
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Right you are tvad. So long rca interconnects are not the solution. But I don't like using long speaker cables either.

Rule of thumb is long IC's are better that long speaker cables. Move your source over and hook it up with cheap Canare:
If it solves your problem you can take your sweet time researching better cabling.
I would try the springs under the table before all that work, myself.
Simple $30 Nobsound spring fix vs complicated expensive move everything around see if maybe that works. So of course we are running 3 against one in favor of what we know will only spend money without producing the desired result. Springs would not only eliminate the problem but be an improvement. OP should definitely read the springs under turntable thread. But will he? 
First off, what is the room construction?
Basement, 2nd floor, interior/exterior wall?
All of these affect transmissive coupling.

20 foot unbalanced interconnects with a low impedance output pre-amp into 10x amp impedance will be fine. Canare Star-Quad with screen connected at pre-amp only is excellent.

Short speaker cables are almost always preferred over long. Increasing diameter only helps R, the least worrisome of LCR.
I’m not buying the long 20 foot speaker wire degradation issue. I have 50-75 foot daisy chain runs of 12 gauge copper to my super high end outdoor speakers and they sound phenomenal. Or buy anti cable - they tested identical in long vs short runs.
That's because all the most rigorously controlled experiments prove the best most efficient geometry is daisy chain. Especially when used with super high end outdoor speakers. A few listeners claim to hear slight degradations but they were using super ultra crazy higher end indoor speakers, and also not properly double blindfold testing. My one question is how were you able to daisy chain cable and anti-cable without them annihilating each other?
The rumble could simply be the fact that your tt bearing is worn, which means changing the cables will not make a difference.

As for cables, both for speakers & interconnects, the shorter they are, the better they are.

@louisl I can confirm that the Nobsound springs that @millercarbon recommends fixed this exact problem for me. I was skeptical but after trying EVERYTHING to eliminate the rumble the springs actually worked. Good luck! 
The key to eliminating tt rumble is 3 things...Isolation Isolation Isolation. You simply cannot isolate enough. Mounting a tt on an exterior wall away from the speakers usually does the trick. I have had great success with this in addition to using Sorbethane  cones under the shelf and used cork isolators under the tt  feet.  I am also big on short as possible speaker cables and long runs of "Balanced" interconnects. I have monoblocks and have used this method for years without fidelity loss of any kind. 
Good luck
Richard Vandersteen has actually tested this theory not just offered an opinion. His results are shortest speaker cable you can possibly run. If you need long runs make it the interconnection cables to components.
I have my turntable set up in what most consider the worst possible location, tucked into a corner just behind and to the left of the left speaker. To make matters worse the table the TT sits on, sits on a suspended wood floor of the second story of a 120 plus year old house in a very small room and I have a penchant for playing loud, bass heavy music. I solved my TT feedback issues with a Townshend audio seismic  platform. No fuss, no muss, no long cables.
Conventional wisdom is to use long interconnects, rather than long speaker cables--the theory being that long runs will do less damage to low signal than high/amplified signal.

I put the theory to use in my 1st house, where the big Vandersteen 4 speakers (each w/integrated dual 12" push-pull sub) was located ~25 ft from the source hardware. As the 200 WPC SS amp for the subs & tube amp for mids/highs were located as close as possible to the Vandies, but off to one side, that meant:
  • 2 X 25 ft runs of interconnect 
  • and ~9 ft. pair of speaker cables 

The resulting sound was amazing. Once I heard that, I never thought twice about the wisdom of my cabling.

BTW, it does make sense to make sure your interconnects have relatively low capacitance--as that is one spec that definitely "accumulates" w/greater length. My interconnects qualified, plus I knew they sounded great from previous experience.
With single ended (non-XLR) interconnect cables, you are in more of a pickle. XLR is designed for longer runs, single-ended ICs are not. 

Longer speaker cables impact the sound. Shorter the speaker cables, the better.  Long runs of quality speaker cables can be expensive too. 

As suggested, isolation. Worth more exploration, granite slabs, layers...
If your preamp had xlr output and your amp xlr input, use longer xlr interconnect.
How long is long? 5 to 7m length speaker cables is still manageable. Some amp manufacturers such as Naim actually recommend to have longer speaker cables for optimum results (better sound).
My one question is how were you able to daisy chain cable and anti-cable without them annihilating each other?

This is funny!  Sorry to quote you twice in one day...I'm not stalking.  

+1 that balanced interconnects are the solution here.  

Given the obvious advantages of balanced/XLR, I wonder why more gear just doesn't have it. Even if it's not fully differential through the unit, the signal transport is far superior. I know, it probably depends a lot on the preamp design...

One other point - Tascam and Henry Engineering make some pretty good quality single-ended to balanced converter boxes. You might not want to use them permanently but it's a decent interim/testing solution to see what kind of degradation you're getting from single-ended runs and whether a balanced connection would be optimal.  

I think the standard recommendation for ”long interconnects/short speaker cables” first came about back when everyone was using tube amps and zip cords. I’m not so sure it’s as important with the ss amps and the heavier gauge speaker cables often used today.
I have run both setups extensively, due to different living circumstances, once with long (20+ ft) interconnects and now twice with long (20+ ft) speaker cables.
I very strongly recommend going the route of long speaker cables. You can run long interconnects (better if balanced, but can do single ended) and there is unlikely to be any trouble at all.
However, the signal is its most robust when in the speaker cable and I now run 25' speaker cable and could not be more happy with the sound and cannot tell a lick of difference.