I am using 128-bit WEP. If you plan to use it for internet radio, or any of the streaming services that have been popping out over the past two years, you can specify which port(s) you want to allow in/out traffic.
Ideally, I'd like to have a dedicated "server" for the squeezebox. Low consumption, quiet, "headless"... a mac mini or something similar. I haven't explored options in a while.
I've never heard of Unirex. I think Squeezebox is a safe bet, having recently been bought by Logitech. Open-source, large developer community, ability to control through various devices, most recently including iPod touch and iPhone, which is killer.
SLIM DEVICES FORUMS. Go here for more information than you can shake a stick at.