Ever since I played Shambler's Castle for Doom 3 I've been thinking I could go for more of that. I have not been playing Quake in steam so ignore my hours.
The original game and the old engine? Revolutionary at the time, pretty dated now. And it is lacking easy customization and some out-of-the-box options. Got questions? There are great guides on steam by Johnny Law. I went with this (which uses the Darkplaces engine):
http://www.moddb.com/mods/quake-epsilon-build/downloads
http://www.moddb.com/mods/quake-hd-pack-guide
I pulled the reshade and id 1 files not in epsilon from the hd pack and stuck it with epsilon, worked great. Possible I made some conflicts but I haven't noticed any problems. All I did besides that was tweak the reshade to my taste. There are more vanilla engines/looks if that's what you want, and they look and run nicely from what I've seen. HD Quake is nice and easy to set up thanks to these mod packs.
Music is easy enough to find, different solutions are around the web. With darkplaces at least, you can just have ANY ten .ogg files in a folder named music inside id1 as long as you rename them track02 to track11.
Quake really is a classic. Loaded with atmosphere and great levels, lots of custom maps. Its a great deal for the regular five bucks but goes on sale semi-regularly. If for some crazy reason you are on the fence, the epsilon build is packed with the shareware levels. If you missed Quake for whatever reason, do yourself a favor and give it a try.