Certainly a pci soundcard is an option. I was reading about ways of connecting PC's to audio systems over at the audioasylum forums, and they seemed to think that internal soundcards are inherently flawed due to their close proximity to so many electronic components.
...I'm thinking the guys over there might be a bit more picky then I am. I suppose it makes sense to try out a decent pci card before dumping much cash on a external DAC.
-- my setup --
Axiom: m80ti(2), vp150, vp100, qs4(2), hsu vtf-2
Harman Kardon: avr-630, dvd22