If you can get a 7200 rpm internal drive, go for it. An ext firewire drive is also smart. They're making bus-powered drives turning that fast, but ya gotta shell out right now. They'll come down eventually. For 2 tracks, I can't see a whole lot of problems just using the internal drive on a digi-approved laptop with an Mbox. It's not like you have to use a bunch of plugins. Just get good sound, and tweak it at home. There's tons of info @
http://duc.digidesign.com