Yes - Firewire has about twice the transfer rate of USB 2 - the cards are pretty cheap if you have a spare PCI slot in your PC.
I like the mbox, and Pro-tools, although it does run better on a Mac in my experience, and you don't get full functionality with the mbox, but at that price I guess you wouldn't expect to. I use a roland breakout DI at home, and that's USB and works fine.
As an observation, more RAM would probably help you out - 512 is kinda a functional minimum these days - you'll have a happier time using it if you've got more....
Just so I've said it, if you're looking at the mbox, have you checked out the focusrite sapphire?