I've started looking at something like this for myself. One program I've seen that caught my eye is Otto (http://www.cardhouse.com/otto/).

Haven't gotten a chance to install it yet, but most of these mp3-database things are all alike, just differing schema. This one is web based, not telnet or cmdline driven, but its mostly Perl, so given time a cmdline client could probably be hacked together.

My only issue is how the playlists link up (still looking at that) and empeg syncing (unlikely to find in any tool,but if you've built up a database, might as well duplicate it on the empeg). I'm looking at mlord's empsync to try and couple it with a MySQL database to grab playlists, new tunes and such.