I've done quite a bit of work with a powerbook G4 and a 002r. I'm not too sure about PCs, I've never done much audio with them, but I found that getting more RAM is probably more important than worrying about getting the fastest CPU on the market. Obviously more of both is best, but there alot of folks selling laptops where they concentrate on advertising how good the CPU is, and save money by not putting as much RAM in the machine. The minumum for LE I believe is 512. I have 640 in my mac (128 built in + a 512 stick to upgrade) and this was enough to keep the system nice and stable while recording. Mixing down is where CPU power really comes into play, so you really need to decide where you're going to put your money.
I don't know if you've bought your 002 yet, but if not, I would advise going to a reputable dealer and making sure the either test for the power harness problem first (I belive this can be done) or provide you with a spare harness and installation instruction for if it does happpen.
My modest rig, until I sold the 002r, was:
G4 Powerbook, 1.2ghz, 640mb RAM
Behringer ADA8000 => Lightpipe
DBX 386 dual mono pre => S/PDIF
ramdom good quality HDD cases with maxtor and seagate HDDs (I've got a few).
I never had a problem with the system as such, only the 002 powere harness problem, which is why I eventually decided to ditch the 002, but that's a whoooole 'nother thread.
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