I have that Amp
I am using it with the 970 though, not the 990 and I have been more than happy with the improvement over my Yamaha 1500. I have had it for only two weeks and I have been making my way through my CD collection again because it really is like hearing them again for the first time; I had no idea what I was missing.
I really wanted the 990 but it is big, too big to fit in my present AV rack unless I place it on the top shelf. The 4-zone bass management is very nice but now that all 5 of my speakers are matched (LCR's) I don't need this feature. I wish the 970 allowed you to rename you inputs like the 990 or my 1500 did. It has plenty of features but so did my 1500, I upgraded for the sound quality and have not been disappointed.
Check out the Outlaw Website Owners Forums; a wealth of information for the prospective buyer can be found there, they have comparison charts between the 970 and 990 and other Outlaw products.
Outlaw is very responsive to user needs and problems. About two weeks ago a couple of users were reporting problems with the 970 & "white flashes" on some types of displays. After a couple of owners reported this problem Outlaw immediately formed teams here in the States and in Asia to investigate this problem; they were able to re-produce the problem and had a software fix download on their Website for this problem within a week. Another good feature with the Outlaw Pre/Pros, like many today, is the RS-232 & USB (990) port for applying this software fixes. Outlaw listens to its customers and takes their suggestions and problem seriously.