Need 25 foot interconnects

As others have mentioned, the starquad configuration is best for a noisy environment. Canare L-4E6S is the very best because the shielding is the best: heavy, braided, pig to work with. Mogami is almost as good, but the shielding is twisted, so not quite as effective, but a whole lot easier to work with.

Add some decent connectors like ETI or KLE and you can't do much better. Switchcraft is pretty good too, for that matter, at bargain prices.

Belden? what kind of cheap monoblocks do you have to use that crappy cable?

Nice gear shaming @urbie -  however solid gold cable also seem to obey the laws of physics.

Spoke too soon about no hum.  It got really quiet in the house tonight and had a good listening session and left the earlier comment where I said "No hum. No noise."  When I stopped playing music and stood up, I heard a slight hum.  I got closer to the speakers and they just have a monotone hum coming out of them.  Going to need to troubleshoot the hum this week and figure out the cause.  Lots of things going on that are different -- also switched from low level subwoofer connection (interconnect) to high level coming off the speaker binding posts, so not sure if it's the 15' interconnect or the high level subwoofer connect that is causing the hum.  Maybe the hum is making the soundstage better.  ;-)

This is great.
Great to find this out now.

Is it easy to run an extension cord to the mono block?
That “test” could allow us to determine if the monos are on a different circuit.
Or you can flip breakers to work it out.

Your trouble shooting plan sounds good.

I will be transitioning my setup at some point next year and face a similar question. I’m currently using a long(ish) pair of WyWires platinum IC’s (13’ single ended) but will need at least a 30’ run in the new setup. The rest of my system is (mostly) connected up with Empirical Design IC’s and PC’s which I have used for decades and never felt the need to upgrade. I reached out to Karl last week to discuss and am confident he has a solution for my new configuration. ED cables tend to fly under the radar but recently won another Editors Choice award from TAS after doing the same in back to back years (2008 & 2009 I believe) FWIW. These are very high quality cables that are reasonably priced and therefore a great choice when you need a long run that could otherwise break the bank (the WyWires are great but considerably more money). Give them a call—Karl has been a trusted adviser for me over the years and is great to work with, customizing lengths, assessing system hiccups, etc.

Hum is more frequently a grounding issue than noise picked up by shielded interconnects in my experience.

A quick test is to float the ground on your components, particularly the amps, and see if it goes away.  If it does, it’s not your interconnects.

Just use ungrounded adapter plugs or pull the ground pins temporarily.

@nymarty 

 Will try Blue Jeans Cable but wondering if there are other companies that can do that length. I suppose I can also try DIY.

I have purchased all of my Canare L-4E6S RCA interconnects from Redco.  Just order what you want on their online order system and wait a few weeks for the build.  Very reasonably priced and high-quality workmanship (I know, it's just an interconnect).