I agree that soulseek is great when you are looking for really niche stuff (but if you can buy it on bandcamp or somewhere else, it's important to support the artists :) )
sephi.zophar.net doesn't seem to work. Not sure what the link is supposed to go to.
That said, if you're willing to use music players and/or plugins that let you play native videogame music formats, you can make use of the music that the main Zophar site offers, in such formats as NSF, SPC, GBS, and others. (And for older systems, these files have way smaller filesizes than MP3s.)
Weird, for me it shows an old html-lookin page with the same stuff as zophar.net/music (Almost reminiscent of emuparadise). Of course I didn't know this before since I'm pretty unfamiliar with Zophar as a whole at the moment.
Using the native formats sounds neat though, I personally can't see myself doing that but it's something to think about.