Have you considered building it yourself? You can save quite a bit and flight sims generally work well with quads as there are so many independent items to keep track of. Its not that hard i built my first one a few weeks ago.
If you use the format shown in the 'how to ask for new build advice' sticky at the top of the forum you can get a superior system for less than either of those would cost you and you wont get the screwed up power situation that those two have. You should have more than 400 for a 4850 and dont need 650 for a GTS250.