eliminating hiss from carputer?

Haem & IAAI: Thanks again for the comments... it's a bit off topic, but I was looking around at headunits with USB inputs, to see if that would help, but it seems that they only really support MP3 players or mass-storage devices, not computers, so that's a bust. As for the PAC unit... the gain is not so much of a concern for me. Using my computer as an audio source is already noticeably louder in comparison to my current setup, so I'm more than satisfied with it. The only hesitation I have about ordering the PAC unit and trying it out is just that: I have to order it online. Perhaps I'm a bit behind the times, but I still like the brick-and-mortar shops. About the 1/4"-XLR adapter... I think that would work, but it'd still require a few adapters in the process... I've got four options as far as outputs go on my DAC: S/PDIF, 1/4" balanced outputs (left and right channel), 1/4" unbalanced stereo headphone output, and a wierd MIDI jack (which I don't really know anything about). Still, it'd cost me $50, plus adapters, compared to $17 for the PAC unit. I'm considering getting a Pro-Ject USB Box to mount permanently in my car, as it uses RCA outputs for both channels, so I could get away with running the PAC unit without any additional adapters. It looks like Crutchfield.ca has the PAC units in stock, so I'll order one tomorrow, and hopefully it'll work out.

If the PC is noticeably louder than the other sources, you may want to connect it backwards and take advantage of the reduction.  Either way, let us know how it turns out.