neal it's really not that hard. i set up a streaming mp3 server here at school for our radio station that runs on windows. that will probably be the easiest thing to do. i use a shortcast server (free) and a program called Simplecast (free trial i think, $60 to buy) but you can find something online that will let you do it for free. of course youll need a computer and an internet connection. the comps that you are lookin at are really sweet, id love to get my hands on one of those, but really the most basic computer will do, the only thing that the software does that would effect the computer is encoding to mp3 from the input of your sound card. if i were you id get a semi-cheap laptop, get a new soundcard (not too expensive, just better than the OEM one) and use that.
im assuming that the venue/bar/etc has an internet connection they would let you use. i wouldnt count on using wireless b/c its much more flaky than just running a long cat5 cable. that would be your best bet. the shoutcast server is really not to hard to set up (its an .exe file) so all youve gotta do it run it and edit the config, and the MP3 server just runs on top of it. i would stay with windows, things get alot more complitcated when you more to linux etc
here are some links:
http://shoutcast.com/download/serve.phtmlhttp://www.spacialaudio.com/products/simplecast/simple cast is really cool and works great. just dunno if you wanna spend money...
let me know if you have any questions