You probably don't have to be worried about the 990 being upgradeable via downloads, at least for software related issues. That's why there is both a serial and USB port on the 990, and I seem to recall that the Outlaws were specific about the use of those ports for both upgrades and remote control.
Of course, no brand can avoid the "back and forth" if the upgrade invovles hardware. B&K is famous for that -- some of their upgrades have cost more than the entire price of a 990!
The Ref 50 is a great piece, but for the price you're doing the right thing in keeping the 990!