I guess its all about what you're planning to do with it.
Mine's a pentium 3ghz with 1GB ram and a Gefore 6800GT GFX card. Im a happy man since.
I've yet to see a program (game or otherwise) that doesn't work, or requires lower settings than is required.

And if I may give you a bit of advice, don't look at the highest GHz. If you need to choose between a few extra 100mhz or 500mb ram, take the extra ram.