hey kross
first, protools or any of the other usual software suspects(performer, logic, cuebase) aren't suited for what you wish to do. LIVE seems like the only thing out there perfectly suited for "live" performance.
you can assign a sound to an individual key( on a piano type keyboard) easily with live. for a cheap controller ( midi piano type keyboard), midiman makes the oxygen-its about 2 octaves and each key could trigger any sound or sounds you assign to it. believe me, on stage you don't want to use a mouse-how accurate can you be? and how geeky do you want to look?

( and lets be honest-we want to look cool on stage...) the oxygen also uses usb so you don't need a midi interface-sweet. you will need a sound card to get the audio out of your mac and to your mixer or the soundman-the options are many-and the prices vary greatly. if you have the $, i'd use a firewire audio interface. clean, easy and reliable. ableton might recommend some on their site. the 896 from
www.motu.com is getting rave reviews though it isn't cheap.
hope this helps. also, if you're using tempo specific loops you'll have to have your drummer playing to a click track which is another hurdle. its not tough to do but its a lot to wrap your head around all at once
