Yes, that would probably be the best thing. When around are you expecting it?
Buying a new graphics card wouldn't necessarily make the emulator faster; both your main processor and your RAM are quite old. Graphics cards can range to cheap to fairly expensive, but if you buy a cheap one you're really just going to get what you pay for.
There's also the problem of compatibility. Your motherboard is, again, very old and you'd have to find an AGP or PCI graphics card, which are both outdated. Pretty much anything you're going to find at traditional hardware stores are not going to work with your computer.
As Momi said, it'd be better to upgrade your processor and RAM, but you'd have to find ones that would actually work on your motherboard.