2 channel home theatre

If your system sounds good to you for 2 channel music listening then it should be fine for HT as well. The only real gain, in my opinion, would be the addition of subwoofer for the .1 effects channel that never seems to be quite right without a dedicated subwoofer especially from a blu-ray disk. As for a home theater processer, I can't see how spending a ton of money would really make a significant difference. The Audyssey stuff wouldn't be nearly as important with a 2.1 setup as it is with five or more channels, again my opinion.

Something similar to the Integra DHC-40.2 ($1,200 retail) should be more than adequate for a 2.1 setup.

Another interesting solution might be the Denon S-5BD (retail $1,800) that is a receiver/blu-ray player that you might be able to "cheat" a bit and use the front high pre-outs to to run into your existing amplifier and let Audyssey correct it to be the only speakers, other than the subwoofer, connected. It might be possible to essentially use the pre-outs as a HT bypass, but I'd confirm with Denon before making a purchase. The price is a little above your stated price range, but it was be two components if you don't already have a blu-ray player.

A .1 is a must. Many great subs out there and it will add a great pick up in the sound of your speakers.