I've been playing with a fender fm212 the last couple years. Its a good amp, it may not be up to par with the big time tube amps, but hey i'm not making enough $$$ now to spend 1000 or more on a guitar amp. I want to build a good rig thats a step up from the fm 212. I"m gonna build a cabinet with probably 4 12s, maybe smaller. Any suggestions to a good preamp and power amp that kinda has that greg ginn sound or more aggressisve? i guess what i''m lookin for is a really tight sound with lots of distortion
sounds like a good idea on paper mate but the trouble is that rigs with separate pre amps and power amps are often geared towards wealthy professional musicians and thus it will be very hard to get a solid distortion on a budget

what is your actual budget sorry? you said that you didnt want to spend thousands of dollars but you never said what your actually willing to spend
It is not hard at all to build a good rack rig for $1k. Look into Rocktron Piranha, Mesa/Boogie Triaxis, and ADA MP1 preamps for tube based units, and Boss GT8, Line 6 Rack Pod, and TC Electronic G Major for solid state units. For a power amp, look into the various offerings of Mesa, VHT, Marshall and Peavey, all of which make solid choices. Remember though in a rack setup all your drive comes from your preamp as the power amps are meant to run clean, so listen to clips and try as many as you can.
I have a preamp/power amp setup too, it's SO much better than my lil' 15 watter.

I use:
an 'Ultra Linear UL2200D' 400 watt power amp matched up with a pair of 'Realistic' cabinets, which each contain: 1x2", 1x4", 1x1.5", 1x6" speakers. And for the preamp I use a Digitech RP-50 (I'll get something better later ).

The bass response is incredible, and the tone I get from this setup along with my Godin Freeway Floyd is very pleasing .

So I definitely reccommend it