Anyone tried the usb/firewire interface bundled with Sonar 7 Producer Edition? Thought? How does it compare to the other alternatives available?

Sonar seemed to get praise but mainly for the software not once did I see mention of the hardware interface ..
This may be a nood question but If my sound card is crappy can I still expect to get low latency if I get a good interface, such as the Power Studio ..Because I would like to record new tracks while playing back the recorded ones, would this be possible without a decent sound card but a good interface?

Also what kind of a digital input does Power Studio have? Because I plan on recording directly from a Boss GT-8 which has coaxial SPDIF outputs ..