I think the actual performance increase of RAID0 is questionable. I'm willing to bet you won't notice any performance increase in games, and you'll notice little performance increase with Windows in general.
However, if you're going to get two drives, why not RAID0 them? As someone mentioned, the only risk is double the chance of losing all your data. Might want to backup the important stuff.
RAIDing two 7200.10 drives would be fine, RAIDing two 7200.11 drives would be better.
It's your call! Good luck!