Well, here's just an opinion. If you're trying to do this relatively inexpensively, here's what I'd do. If we're just talking about drums, you could get two channels of outboard preamp and run them into the 002R somewhere there isn't already a preamp (channels 5-8, spdif, lightpipe, etc). Then, you could go ahead and use the 002's preamps on channels 1-4 to make up your six channels of input. When you're recording more dynamic sources (acoustic guitar, vox), you could use the better quality preamp channels for those.
As for the preamps, do a search here for ideas on that. Two ideas for a cheap, good preamp: The Rane MS 1b can be found for as little as $133 -- you won't find a do-able channel of preamplification for much less than that (by "do-able," I mean a preamp that will more or less get out of the way of your better microphones and not add noise to the signal chain). If you're looking for a full plate voltage tube preamp, and you can DIY in the slightest, you might consider modifying something like a Bellari RP 503 ($179) with a NOS vacuum tube and Burr-Brown opamps (do a Google search of "Bellari RP 503 mod" and you'll find details). Those are the two cheapest possibilities I can think of. I'm sure everyone and their brother will have an opinion on a preamp for you, from Aphex to Yamaha. Happy hunting.
Boog.