I'll speak for Glen, since you know he's going to suggest the Pioneer VSX-711 😀
What are you upgrading from exactly? And what will you be using it for...more music, or more movies? Do you need any special inputs capabilities? (Component switching?)
For around that price, I'd say the H/K 320 (which I have myself), Denon 2802/3802 (if you're lucky, you shoudl be able to find a 3802 close to your price), Onkyo 600.
I gotta say that I love my H/K...it's rated at a lower wattage than the others I listed, but I bought it because people on the HTF said the power was cleaner and would be more suitable for music-listening. That being said, it had no problem driving my Paradigm Monitor 9s...and it does even better with my Studio 40s now.