I don't think that the Athlon 64 X2 4800+ would bottleneck your graphics card too much. Depending on your budget, I suggest you upgrade to a Radeon HD 5750 - equivalent to a GeForce GTS 250, aka a 9800GTX+, which is more than twice as powerful as your 8600GT, possibly three times.
If you want to max BFBC2 at decent resolutions, then you'd need something like an HD 5850 at least.
Wow ... you guys are awesome, I've never gotten so many useful responses from any other tech forum.
I have a 500watt psu. And if by native resolution you mean the resolution I use for my desktop, its 1280x1024. Sorry that info I left that out.
If I had a budget of $120, what cards do you guys recommend? (I dont NEED to max out BC2, just want more smoothness) Also, since hearing that my mobo -luckily- supports a newer bios, should I upgrade my CPU?
I'd get an athlon II x3 435 or athlon II x3 440, depending on whether or not oem is ok for you. Or, just go for a athlon II 635 since it is at good price right now. 8600 gt? That is not bad, what res do you play at? Getting 4GB of RAM would take priority I think.
The best choices for a card in that price area are the HD5750 and HD4850. The HD5750 is about 5-10% faster, much more power efficient and DX11 compatible but it is also costs $20-30 more. Both should be great for your resolution.
Upgrading the CPU is something you definitely should do but if you can't afford both right now the card is probably what you should get first. Your CPU will hold you back some but not nearly as much as that 8600GT.