Looking to upgrade speakers..need help/advice

[kingtuna]

Hey all,

So I'm considering upgrading my 7.1 speaker set up because I think that the center speaker doesn't really output that well. First question: Does it make sense to just replace the center speaker and keep the others? Or should I get all speakers to match from the same company, etc?

My current setup:
Sharp Aquos 46 in LCD
Sony DG910
Onkyo Sks-ht540 (7.1 speaker system)
PS3 60gb

I don't really know how the whole speaker ohm matching goes (6 vs 8) and if my receiver needs to have the higher capacity ohms or my speaker, etc. I'm in an apartment building, and I have an ******* neighbor in a studio apartment above me, so I can't go too loud.
After reading some other posts, it seems as though Klipsch or Paradigm is the way to go. I've also read that some users like Polk Audio. I'd prefer to buy off of Amazon as they tend to have the best prices, I have prime, and they don't charge sales tax (thank god, I don't live in NY). If you have any specific model numbers, that would help me tremendously.

Budget wise I'm looking to spend probably no more than $500. Also, does anyone want to buy my Onkyo speakers if I decide to upgrade (I bought them new in December 2007). Or should I wait for a specific time of the year that will have deals on speakers?

Any help, advice, recommendations, or preference would be greatly appreciated. Thank you.


King TUNA