Short answer: get a Receiver. "Trust me."
Long answer: The Rio Receiver is, essentially, a simple little computer that pulls audio files off a server and plays 'em, either through a line out or through its own amplifier into speakers.
The client end has a decent interface (though not without its shortcomings), letting you select music by artist, album, title, or genre, or by playlists you set up. It receives MP3 or WMA data and does the decoding locally.
The server end is either pretty bare bones but solid (the supplied windows server simply finds and indexes your music for you, then provides a query engine for the receiver to hit) or very full-featured but somewhat tempermental (the JRec project, which allows you to create dynamic playlists, like "select where title like "%christmas%" or "songs added this week").
Get a decent computer (an old 400 mhz box would probably work just fine), and slap in a nice disk drive (preferably, two, one for music and a small one for the OS, so you don't trash your music when next you upgrade). Install windows or linux, copy your music in, and install one of the servers. If using JRec (either windows or linux), you'll need to worry about a database and things like DHCP and NFS, but once those are set up, you can forget they exist. If using the stock player (windows only), it's all "Magic."
Once you get the server software installed and running, plug the Rio into your network. You *do* have a network, right?
If not, the Rio brand (not Dell brand) comes with an HPNA card and you can run it over your phone lines. Turn it on, it'll find the server, download its software, then in just four clicks and one twist, you can have music playing. It's that simple.
With the windows server (I believe, I've always used the Linux ones), you can use any regular playlist editor to make playlists (like "Party Mix" or whatever), and the server will make them available right on your box. So you configure it in the back room, but use it from the bar.
Does this help? Read around on the board here, and I'm sure you'll get a better feel for what it does and how it works...
david.