How can power cords make a difference?

I know this is the wrong forum for this (not sure which one I should present this in anyway) but it seems there are a lot of extremely knowledgable people in this forum and since I sorta have your attention here goes:

I'm placing myself before you on how/where to proceed in improving my modest audio/HT system. It is as follows:

Sony 36" TV (no component vid, just S-video)
Harman Kardon AV500 (70w X 5 channels)
Sony DVP-S3000 DVD
Denon DCD-2000 CD (RCA's to HK)
Carver M400t
JBL L100's (for left/right)
JBL TLX-Center2 (center)
3 way in-wall JBL's (for surround)
Dahlquist 12" sub (150 RMS, 400w peak)

The HK L/R preout drives the Carver M400t while the HK's own internal amp directly drives the centers/rears (of course the HK's sub out goes to the active sub). My 'theory' is if I use a seperate 'L/R' power amp I reach an acceptable compromise between my (2 chan) music and (5.1 chan) HT needs. Sound levels are balanced to within 1 Db using sound level meter.

All interconnects are optical or S-video where possible. Pre-amp to power amp interconnect is heavy Monster cable (RCA's). Sub out to sub is heavy monster cable (RCA's). Speaker interconnects are 14 ga stranded monster (tinned wire ends). Power cables are 'stock' ;)

All components (except Carver) sit in a rigid 'entertainment center' constructed from 'formica like' covered 1" MDF. Shelves are same but 5/8" (and themselves sit on small adjustable 'pegs'). No isolation/damping pads used. Carver sits on (non pile carpted) floor. JBL's sit on oak topped steel legged tables to raise them to ear level. They are spaced (approx) 8' apart and L/R & center is within 2" of 10 feet from the 'sweet spot' listening position. Rears are (in-wall) approx 11' behind and 6 1/2 ' from the floor.

I believe my next 'big' investment (everything is relative ;) is to fully re-cone my L-100's ($600). While they're sounding good and otherwise in good shape, just the fact they are 20 years old leads me to think it's getting about time. I just love they way these speakers sound which prevents me from thinking of replacing them entirely. I just don't think I could obtain better range/imaging speakers for a similar cost. Thoughts?.

One of my current dilemmas is while the rears seem fine, the (newer) JBL center speaker (while sounding fine on it's own) doesn't match the umm.. rich 'tonality' of the L-100's. Not sure how to resolve this (short of just trying out speaker after speaker).

Another quandry I face is my 14x20 'media/living' room (in a small condo) is rather bright. At louder volumes (-5 to 0 Db) I'm getting all sorts of reflections and often higher freqs seems to 'resonate' at times (resulting in my suddenly paying more attention to the 'defect' than the music/movie). At least I think it's the room that is causing this since lower volumes (-5 to -15 Db) doesn't seem to produce the 'resonance'.

So, anyone have any suggestions how I might 'evolve' from this point? How I might improve this system and/or sound (considering I'm on a pretty tight budget)?

Any advice/suggestions will be VERY much appreciated.

Other than room reflections, etc. if you like the sound of the L-100's why not try and find a single one for the center channel and then have all three refurbished at once? I don't do HT myself but have listened to some otherwise nice setups in which the center channel did not match on vocals very well.

Jhunter has received the test power cords from Purist Audio, and this morning I emailed him to be certain that they arrived in good condition. I am hoping that before too long, Jordan will have a complete report.

chance to listen yet? Curious to hear what your thoughts are.

Mmccoy, your skepticism is well-placed. The expensive power cables are audio fashion, not audio performance. The purpose of a power cord is to transfer AC power from the outlet to the audio device. A very simple commodity-grade task, but there's little profit margin in commodity-grade simplicity. Thus, the hype, the snake oil, and the megabuck power cables.