I use the mackie onyx satellite as my external soundcard for my macbook. I run the firewire in/out of the laptop and run to my amplifier out of the onyx. I have a pair of mics rigged in my room, as well as a pair of TRS ins that just live in the base (guitar/bass through stereo effects unit). Then of course I can just pull out the satellite and take into the field. For a while, mackie was running a rebate where you could get a carrying case, extra power supply, and extra firewire cable. Makes life super convenient....my R-09 even fits in the case with a 1/4 pair to 1/8 stereo cable.
These originally sold for $300 or $400?, but after about 6 months of being on the market, they were discounted to $200 and occasionally dipped down to $160. DO NOT judge the quality on the price. I have gotten lots of use out of this device, and although I rely on my R-44 now, this unit gets plenty of use, as my final mixes and everyday audio go straight through it to my ears.