SSD for the OS / boot drive would be my first upgrade. CPU cooler (Hyper 212) with a good overclock would be the second upgrade. Then maybe PSU to pave the way for crossfire??? Not sure what your PSU is... If the case isn't ugly or too big and you can "live with it", then no need to spend money there.
Dang, forgot to include that in my specs. Its an XFX 650W Black Edition. Thanks for the responses. I do intend to get an SSD at some point, or perhaps a WD Velociraptor, but I'm going to wait for prices to drop, also a friend of mine has had 3 SSDs fail on him in the course of a few months, so I'm going to hold off. Definitely a priority though.
The CPU cooler looks awesome, would probably prolong the life of my parts, too. The case is very old, it rattles a lot when the hard disk gets spinning, and it doesn't have a whole lot of cooling options (no extra grates for fans), but I suppose I could live with it.