Which "tweeks" are more important

In line with your thought to try better support for components and speakers, the mini-priced items at Herbiesaudiolab.com are well worth a look (actually, a listen).
To avoid carpet piercing, I support floor standing speakers with Big Fat Black Dots resting on granite or marble tiles from Home Depot. The Dots will surprise you with ability to enable better speaker performance.
The Tenderfoot/feet beneath your components on their existing shelves also are a quick way to upgrade.
Although there is no single answer to what support is the best, these get my nomination for most likely to succeed.
Because these are low cost, money is left over for other ideas already posted.
The ninety day home trial period is enough time for anyone to be sure the results are to their liking.

If you can dedicate, do - and put some Oyaides on the wall to cap it off. If you can't, that's fine too - get a balanced power unit from Equitech or BPT or...

I have also found considerable (but not consistent) gains from various isolation units (eq Aurios, Roller Balls) under source, pre and amp. Not the same for all the units - and even one can make a big difference. Approach this in conjunction with a look at the platform itself - most sound better on a thick chunk of wood, a few on stone. The synthetic shelves are very amazing.

I did all the isolation on my rack shelves which leads me to believe that unless you can get to the really high end, get something sturdy and then start tuning.

Last add has been some Sistrums under my speakers and son of a gun - those help too.

Is anyone using a Monster AVS2000 with a RGPC 400? If so, do you see / hear any improvements?

Portonyl, I'm using the Monster AVS2000 with the Monster HTPS 7000. I find they do EXACTLY what Monster claims they're supposed to do. There're excellent...

Can anyone with first hand knowledge tell me what kind of mess i will experience when installing dedicated lines.
Thank you for all your help and advise