Have $250 -- Get another 6870 for Crossfire or add more components?

Newegg ended up sending me a $100 gift card for participating in that gift card promo last Sunday, and my mom got me a $100 sum of Newegg gift card for Christmas. I'm a college kid home for break, and my comp's back on campus, so I have 3 weeks to work on it, but...

What should I do with that money?

My initial thought was to add the 140mm and 200mm case fans my case (HAF 912) supports, get a Hyper 212 cooler for my CPU (currently using stock), and use the rest of the funds to add a second hard drive or maybe a blu-ray drive or something. But now I'm curious... I got more than I expected (didn't expect the $100 from Newegg, and anticipated only $100 from parents), so now I am in the price range of getting another 6870. I guess my question is this: Would it be worth it? Would framerate increases be noticeable enough to warrant buying another GPU not even a month after the computer was built?

Current specs besides GPU and Case

PSU: 650W Seasonic
CPU: AMD Phenom II X4 955 BE
HDD: Samsung Spinpoint 1TB
ODD: Asus Super-Multi Drive

Would the 650w even be enough juice to crossfire two 6870s? And if the answer is "yes, barely", would I have to get a new PSU if I were to get the other components (more drives, fans, etc.) and then buy a 6870 with savings over the next year?