I want to change from 2 channel to HT but what....

I have a very good Karan KAi180 integrated amp, a diy cd player and Merlin VSM-m speakers. I would like to sell the Karan and purchase a used or new HT receiver or separates. I want to spend around $2500.00 (the used price of my Karan). I am looking at, in this order, B&K 507, Sunfire receiver or separates like the Lexicon MC-1 with a good amp. I have also read some good info on Yamaha, Denon and a new Samsung digital receiver. I have also read that Sony has a digital amp in a receiver as well. The Samsung is out of my price. My plans for the near future is to buy a new Panasonic 50" plasma. I would like the hdmi switching, 7.1 and THX Ultra. I don't think the B&K 507 or the Sunfire has these. I am not realy keen on Sony, Yamaha, Denon, Onkyo or Samsung etc. receivers for the only reason that I would not buy one for a 2 channel set-up, but I am willing to consider everything. I do want at least 170wpc, THX Ultra, DTS, DD, 7.1 and a good video switch hopefully with HDMI. I do believe a good receiver can sound as good as separates. Mybe not in my $2500.00 price range. My Karan integrated was an upgrade from $7500 Melos separates.