Firewire Audio Interface advice needed

[squintylive]

I'm currently using Live on a Mac with an M-Audio Firewire Solo (2 channel) interface, but would like to be able to record up to 4 channels simultaneously. Looking at M-Audio and other websites, the more I read the more confused I am. Can anyone recommend a (preferably small and portable) firewire-based 4-channel interface that will allow me to record, say, two guitars and two separate vocals to 4 separate tracks in Live simultaneously. Descriptions such as 4-in, 4-out, it seems to me, often refer to RCA connections etc, though I'm sure what I'm looking for must exist.

Thanks for the help in advance, and please forgive what might appear to be a very basic question.

[draff]

I use the MOTU 828 MKII, works great. But for something with similar capabilities and a little more mobile, try the Traveler or the Ultalite:

http://www.motu.com/products/motuaudio/traveler/

http://www.motu.com/products/motuaudio/ultralite/