Need new CPU or video?

I was looking into upgrading my main PC for a short boost.
Meaning: I am planning on building a completely new system within a year so I don't need to upgrade a whole lot.
I am on a tight budget, but here's my question: should I get a new CPU or a video card?
Mobo: M4N72-E (750a chipset)
CPU: Athlon X2 5600+ (Brisbane)
Video: Nvidia 8800GT
Mem: 4gb DDR2800
Vista 64 Ultimate

I know and fully understand that there are many things that I need to upgrade, but for now only one can be afforded. Maybe I'll do another one in a month or so.

I really can't seem to decide here. I don't want to get a newer video card and my CPU be a bottleneck. But, I don't wanna get a new CPU (Probably go with the AMD Phenom II X2 550) and it not make a noticeable difference for my gaming.

Main purpose for my machine is everyday use, but I play at least 10 hours of games a day on this machine. TF2, WoW, FFXI, Fallout 3.

Which do you think would make a bigger impact on my PC?

Thank you~

Interesting.

Best bet is to wait longer.

If you upgrade either part, it will bottleneck the other.

Phenom II isn't that big of an upgrade.