I just bought the Denon 3808 and the Kef 5005.2 speaker system all up was $6240.
This is probably out of your budget ? and you also said floor standing speakers.
Before buying my system I was searching the DTV forums.
http://www.dtvforum.info/index.php?showforum=7
There's alot of great information there although from what I can tell not many people using a HTPC.
I'd second the Yamaha option (1800 or 3800), although I just read someone who had just bought the 1800 has to bring it into the shop for a firmware upgrade to rectify some issue with decoding DTS HD MA ?
They say the best "Bang For Buck" receivers are the Onkyo models but they run a little hot ?
Jack