Sampling analog out from PC is actually the by far easiest and best way without getting lost in magic frequencies and stuff. But you really need to make the PC sound sound good in mono first, and you must have a sampler that's quality. I bought mine for 100EUR back in the day, but I don't think the 30 EUR "Radio Shack quality" ones back in the day will make you happy. They have dist, noise, and can't sample as fast.
If you get the classic "studio ground potential" hum, you have to check where it comes from, but a good sampler really can be better than conversion.
I wrote a tutorial post myself a while back to guide people which goes through all the options. Convert using sox to 8-bit, and skip the IFF nonsense, and that's as good as it gets digitally.
I started a converter to pseudo 15 bit for OCS 18 months back , but it's only at proof of concept. It needs to be supported in trackers and players, and I'm still looking for the source of my snazzy wave editor... it's somewhere on my old disks...
Wanted to link to (and read) h0ffman's post, but I guess it's not up yet.