Edirol FA-66 Firewire Interface...

Greetings,
As I used do a bit of casual home recording, I own an Edirol FA-66 Firewire Audio interface that is currently connected to my Dell desktop. Routed through a Mackie mixer, old 2-channel power amp, to speakers.

www.roland.com/products/en/FA-...

As you can see, www.roland.com/products/en/FA-... this is a pretty inexpensive piece of equipment.

Would I see a significant improvement in audio quality if I used something like a Cambridge DacMagic or Benchmark DAC instead?

Also, since I have already invested in a Firewire card for my PC, if I do buy a new DAC... USB or Firewire?

Thanks very much in advance.