I can't speak to the merits of the Bel Canto amps but I have the 990 with an ATI 2005 (same as Outlaw 7500) and I couldn't be happier. I made a move much like you are considering; I replaced a Pioneer Elite receiver with the 990/2005 and the difference was stunning. The ATI has more than enough power to cleanly drive my 4ohm M&Ks and the 990 sounds great plus it is very flexible. Your Polk speakers have some loyal followers in the Saloon so hopefully you will get some opinions on driving them with a 7500/7700.

Before I got the 990/2005 my system was used about 80% of the time for movies/hdtv and about 20% music. Well that flipped around to 80% music and 20% movies/hdtv shortly after the 990/2005 was installed. I found my appreciation for stereo again with the new gear. May I suggest that with Outlaw's 30-day return policy you have the opportunity to test drive the 990/7500 combo in your home with only shipping cost at risk. If you can get a Bel Canto to compare at the same time all the better.

I don't think I have a lot of electronic noise near my HT gear but I still use the balanced connections. The debate running in this forum and in others seems to be whether balanced connections are warranted over unbalanced. If there is a difference in sound quality because of the 990's internal workings I don't remember any discussions about it. So I took a "belt and suspenders" approach by using balanced connections for a modest cost increase. Maybe Gonk can weigh in on the balanced vs unbalanced issue since he just replaced an older Outlaw unbalanced amp for a new 7500.

Bottom line from me is that I think you would be very happy with the 990/7500 combo.