What are you trying to tweak improve?

Sometimes it´s soundstage, others clarity, vibration control
What do you seek more frequently to improve by tweaks.
I have focused on vibration tweaks even for the power conditioner....
As I have an all digital system, two aspects of music that I am very sensitive to are glare and smearing in the upper mids and low treble. But other parts of music that are very important to me are timbral richness, especially in vocals, and also PRT. It's been my experience that PRT can be significantly changed by choices in vibration control.

Minimizing smear and glare and maximizing timbral richness seems mostly related to component (including speakers) and wire choices, and room acoustics. So, it's these properties of music that I've spent a lot of time, money, and effort trying to "tweak". Some tweaks work, some don't, and some make things worse-- maybe that's what keeps it interesting. Cheers. Craig
As I see it, the tweaking is like using a equalizer. Any tweaking method will affect certain frequency(increase or decrease it). My experience is that using hardwood like Ebony or Purple Heart are very effective in altering the sound. When using it properly, it adds harmonic to vocal or any kind of acoustic instruments. Making it sounds very natural, full of life and very realistic in the presentation. Other material like the Black Diamond Racing cone, the BDR shelf, carbon fiber board, grainite or marble slab all have their own character.
In general, hardwoods give the system more warm, musical and softer presentation.
Other materials like BDR cone/shelf, carbon fiber board, grainite/marble will give the system a more bright, analytical, sharper(less natural image), dryer presentation.
Usually a well-tuned system will need to a mixture of the above materials in order to make it sounds nice and balance.
It is like cooking, everyone have their own mixture of spices......
Every time I tweak or upgrade, I find myself listening for improved realism -- the illusion of musical presence. Specifically, I'm looking for clearer highs and stronger dynamics.
At this point, I'm most interested in obtaining the blackest background/lowest noise-floor possible. I believe that so long as one perceives that the other areas mentioned have been addressed, I believe this lowered noise-floor will simply enhance sound-staging, imaging, etc. and add more micro-dynamics bursts and bites from a dead silence to give the music more of that 'live' sound.

To reach this goal (not yet attained), I've installed custom 10 gauge 99.95% OFC romex, three dedicated circuits/lines, aftermarket audio-grade electrical outlets, floated the ground on all three circuits, and am using dedicated in-line power conditioners in place of power cords for each component. The only thing I can think of next is convert my amp from 115volts to 230volts and convert the amp's circuit to 230volts. I'm just too nervous to do this myself right now.

I'm certainly open for suggests.

Mapleshade has some incredible tweeks that live up to
their billing. Talk to Pierre. He knows tweeks!
Turntable base for isolation. I see commercial ones available for $1250 ... and more ... and I nearly faint. I'm working on a prototype, with assistance from engineers at Sorbothane. This is a granite slab (1.25" or 2.50"), on an air bladder, in a wooden frame which is all glued and doweled (no nails or screws to vibrate), which sits on engineered Sorbothane feet. Since the guy who sold me the granite sold me 10 pieces, once I get this tweaked to its maximum potential, I might put some up for sale here. But the results so far are very promising :-)
I got all sorts of tweaks going, but have been recently confused by the isolation tweak. I have my preamp and cd player on isolation points, then had shot on the top to help keep it stable, however I was recently told not to weigh down my components that are on isolation spikes, yet I have seen products sold for just such a purpose. Who is right? Or is this yet another thing in the audiophile world that doesn't have a concrete answer?
Mdomnick ... I'm far from the most technically-able guy here ... but it seems to me that dampening a component's chasis through mass is a time-honored method of increasing its stability and resistance to movement through vibration. This is half of the "trick" of the VPI Magic Brick (the other half being RF absorption). I would think that, provided the combined weight of the component and the added mass are within the weight limits prescribed by the cones' or spikes' manufacturer, that the added mass should help. But your suspicion is correct -- there are very few concrete answers here, and the ultimate judges of the effectiveness of the tweak must be you and your ears.

Adding a small detail to Paul´s comment above if your points are "point up" to the equipment chassis and there´s more weight on top of the unit, too much pressue will be concentrated in the point and might dent/damage the unit
I never used to care too much for cones but recently tried the new Mapleshade brass cones and heavyhats and like them very much. There seems to be something to the theory that brass works best, since when using both cones and heavyhats
I get increased resolution with very little tonal shifting which I found was the problem with most cones previously.

I normally use the two down, one up pattern for cones where the one up carries very little weight and basically balances other two cones. This is discussed at DH Golden cone site and seems to work good for me.

The Mapleshade triple point brass cones work even better, reducing contact area to a minimum but cost is much higher
but still pretty reasonable.

Interesting these Virtual Dynamics AC cords everyone is talking about actually attempt to control mechanical vibrations of component by special design features of the
AC cord connected to it.
I might add that the brass Mapleshade heavyhats do not add too much weight, I usually use 2-3lbs on each component, and edges have been radiused to reduce change of scratching gear.