Hello,
I have a client who has a massive mp3 collection.  We're talking
>500GB and growing.  They have been using iTunes from the beginning
and, for a time, it's worked well.  It appears now that their enormous
library has gone beyond the capabilities of iTunes and it's bursting
at the seams.  I've looked for a commercial grade solution for their
needs but have come up empty handed.

I'm looking for some sort of server software that lets clients listen
to the mp3's located on the server, edit the server playlists from the
client workstations, import new music to the server and hopefully, not
crash when their library grows past 1 or 2 TB.  Is there any good
software that does these things that isn't super expensive?  Thanks a
Ton
Erin

What about this? http://mediaportal.sourceforge.net/index.html
I haven't used it myself so I don't know how capable it is, but it
sounds like it has potential and the price is right.