External sound device vs PCI soundcard

External is definitely better. We use an external ESI U24 for our acoustical measurements. The noise floor is much lower this way--even on a battery operated laptop. I'm not familiar with the one you mentioned, but I would expect it would be superior to an internal. The only other option is that some PCs have SPDIF output--then you could go to a good D/A. I have not done this latter one myself, so there could be some configuration issues (such as sample rate and bit depth), but perhaps other a-goners have done this and can comment on it.

Thanks Rives

Yea, I looked into using an external/stand a lone DAC for 2.1 and 5.1 sound. But here in little old New Zealand it is quite pricey buy one new and there is little in the way of second hand.

I've carried on searching and from reviews I’ve come across I narrowed it down to four contenders. First is the M-audio Sonic Theater USB, second is the M-Audio Revelation 7.1 PCI, thirdly the Terrtac Sky 5.1 PCI and lastly the M-Audio Audiophile 2496.

Most theses cards are in the same price range $300.00 - $450.00 NZ, so if I weigh up the sound quality of the output signal from each card, is it most likely that the Sonic Theater will come out on top because its outside of the case?

Any thoughts.

P.s, just to clarify, the quality of the output signal is my sole measurement criteria. I know that usb sound devices can use added PC resources but with a high end HTPC it won’t be an issue.

If I need to provide more info get more responses let me know.

It's just that most other forums I've visited that deal with PC audio reason that a semi-pro soundcard is insulated against electrical noise and does not affect the DAC, which seems to contradict views on this site.