I have an Adcom GFA-770 (200w X7) paired with the 990 and I'm very happy with it. It does require a 20 amp circuit, which wasn't no problem for me, just replaced the wall outlet as I was already wired for 20 Amps.

One thing I'm sure you've been keeping in mind is how the sensitivity of your speakers, ohm and power rating of your amp. More power is a good thing as long as it's clean.

Good Luck