Mbox vs. Good Preamp

I am considering purchasing an Mbox because it has real good preamps.
It only costs $500.00 which is not much considering it is a good preamp and a digital converter.

My only question is would I be better of just investing the same $500.00 in a preamp?
Can I get a preamp as good (or better) than the Mbox's for $500.00 ?

I've already got a sound card (MAudio AP-192) so I don't particularly need that aspect of the Mbox.