well, you might be able to get a pretty decent board for 4-5k used. call some folks like Pro Audio Design and see what they've got.
meanwhile, if you just divide the $8000 into 4k for mics and 4k for preamps, you've also got possibilites. You could get three SYTEKS for about $2400, which leaves you $1600 for the four remaining channels. Maybe a Vintech 1272 and a couple of cheapos.
but i'd probably do a combination of both ideas - get a board for $2000-$3000,and spend the rest on one or two higher quality preamps.
if you budget the remaining $4000 on mics, i'd get one decent but not too expensive vox mic (like an AT4060)for around $1000, a couple of decent small diaphragms for instruments and/or overheads (Josephson c42's are $1000 per pair). you can get a variety of good kick mic's for around $200 (like the D112
or ATM25). At least two SM57's. Then fill in whatever else you need from the usual suspects from Oktava, Marshall, Studio Projects, etc. that will probably average $100 each. These days you can actually get 16 mics for $4000, which wasn't always true.
But you should ask yourself if you really need 16 mics and pres at first. If you will be recording electric bass mostly DI, for instance, than that might be one less mic you need to buy. You may find you can do quite well with only twelve mics, in which case you cn get better quality per mic.