Sucks, man.
Anyway, just for future reference, I was skimming IGN awhile back and it looks like the 8 gig is out in January and will cost ~$200.
So if you just wait until April, you'll be able to get 8GB of memory for probably $100. Just something to think about.
And believe me, you'll figure out how to quickly exhaust all 8GB on that thing. Hell, I filled up my second 4 gig stick in, literally, 30 minutes. I have 90mb left on each one, and the space is strictly for gamesaves and any future homebrew app upgrades.