Help!!! Getting Back on the Saddle

Hello everyone, I have recently decided to start my project studio back up. at the moment i have no system available since i sold it all, except speakers and program. Now i want to get started again, this time get something worth while. I plan on geting a Mac Pro quadcore, with at least 2TB HD space, and 8 GB RAM. Now my questions come as of what is better a firewire audio Interface or a PCI-e audio interface, or USB. Before I used to have an old Nuendo 96/52, i do mean old, bought it back in 2000, But it was sturdy and reliable. Now I’m not sure what is out there, since i didn’t keep up with the changes that have been going on lately. If anyone could suggest on what i should get as far as an interface goes, a DSP Card, probably going with a UAD2 Quad, I would really appreciate it.

Ok as far as other things go I have 4 Genelec Powered Speakers with Subwoofer, Nuendo 4, and a couple of hardware compressors.

Thanks for your help.