I own the 7700 and I have compared the 9000 and the 7000 to it and common sense dictates the following:
1. If there is any difference (video) in them it is slight. They are all very, very good. Anybody who owns any of them should consider the cost (considerable) against the perceived advantage (slight) in "upgrading".
2. I have heard 2-channel sacd's and multichannel sacd's and dvd-audio and an inexpensive ($400) multichannel sacd or dvd-audio is a better value than megabucks for 2-channel.
3. The future of progressive scan seems to be headed for 720p and beyond. A good scaler would be a better buy than the 9000 for less money (look at MSB's progressive scan/scaler upgrade for the 7700/7000 which offers 480p to 960p! for $899 installed)
Bottom line - keep the 7700, put your money elsewhere or wait for future trends.
Anybody who doesn't own the 7000, 7700, or 9000 can eat their hearts out or buy ANY of the above and be happy.