im looking to get an audio interface and the presonus line has cought my eye, but im curious as to the types of preamps in the inspire and in the firebox.

it seems for 100 bucks more you only get a few more outputs and midi implementation on the firebox, but

does anyone know if the preamps are better as well?

If you're in the market for some more io's on your interface you should check out MOTU:s 828 MK-II or
Traveler interfaces.
Presonus makes decent gear but used to have some trouble providing drivers for the latest OS-X versions.

As for preamps on the respective 828, Traveler, Firebox and Inspire Firepod etc it's hard to say.
It seems proffessionals prefer to use really expensive amps and ad-converters like the Rosettas and such.

I doubt if you would hear any great differences between the interfaces above.
Chances are that the compopnents inside the preamps, are the same.
( the electronics industry and markets beeing what they are )

The general principles for designing a good preamp is well known, even if details may vary.

Cheers: Dixiechicken