I had these on cassette from a trade some years back, and this particular tape was much better sounding than another tape of the demos that I'd heard. When I got a CD burner a few years ago, one of the first things I did was to put these on CD. I recorded the cassette onto the computer as WAV files, ran the files through CoolEdit, and eventually ripped them as .mp3.
CoolEdit is a shareware audio editing program that allows you to "sample" noise you would like to remove from the .WAV - in this case, a large amount of hiss between tracks. This hiss was almost louder than the songs themselves and was audible over the entire tape, a big sign this tape was many generations removed from the source. I sampled the hiss between two of the tracks, messed with a bunch of sampled noise removal settings, applied the "remove sampled noise" filter across the whole thing, and then did some EQing to balance it out. At that point I finally noticed that the tape was about 1/3 faster than it should have been, so I was able to slow it down also using CoolEdit, using the released versions of Ceremony/Truth/Dreams Never End as pitch reference points (accounting for the fact they may have played the songs faster rather then all of them pitch-shifted a whole fifth up the scale).
At the end of the day the final result was orders of magnitude better-sounding than the tape.
I don't think the older shareware version of CoolEdit (CoolEdit 96, I think) that I used is still available, which sucks because it had less features disabled in the shareware release than its successor (CoolEdit 2000) has.
CoolEdit: http://www.syntrillium.com
edit: Found CoolEdit 96 here.