I know this might still not make since to you Xion X2, but I am happy.
Hey man, that's all that matters. I'm just weighing in with my opinion.
If it were me and I still had my GX2, I wouldn't have done it--although it looks like two 7950GT's outperform a single GX2 by a little (which I didn't expect at all. Not sure why?) You could install a 10$ fan or two to blow on the GX2 to keep it cooler instead of laying another 600$ on the table with:
1) No guarantee of a price-buy on the GX2 you already have
2) No guarantee of a step-up to G80.
I realize I'm kind of pissing in the punch here which is not my intent, but I guess it comes from a track record of me making mistakes with money and growing up under a father who has pinched pennies all his life. Hell, I've pissed away money plenty of times, too. I bought two sportscars in a span of 2 years once. We all do it.
Have fun with your new setup. Hopefully eVGA will let you step-up when the G80 hits store shelves.