Powerbook Audio "Middleman"

[ChitownE]

Just got a new Powerbook and also purchased these mini studio monitor speakers from Edirol:

http://www.edirol.com/products/info/ma10d.html

The sound is great, but I'm wondering if there's a way to take it up one more notch. Is there any type of external soundcard I can put between the Powerbook and the speakers to boost sound quality? Would things like these do anything?

http://www.m-audio.com/products/en_us/Transit-main-1.html
http://www.edirol.com/products/info/ua1x.html

Thanks,

~ Eric