Would it be theoraticaly possible to make an external hard drive that utalizes dual USB 2.0 Ports, a USB and Firewire or Dual firewire ports? Would these out perform a SATA?
I'm going to say that it is theoretically possible. However, its practicality is very doubtful.
You would need some specialized hardware on the enclosure in order to take in both input streams and process it to the hard drive. In addition, you'd need specialized drivers on the OS level to make it feasible and so that the OS won't freak out.
All in all, you'd eventually just end up being limited by the hard drive itself.
Better (and more cost effective) options:
1) get eSATA
2) research external HDDs and make sure you get the fastest transfer rate you can get/afford.