Dirrty drums evolve around a dirrty room, so: Add some room and try your battery 12 bit thing again (you might not even need it). For the room try some soft slapback or early reflections with timed predelay to get some grain in. Experiment with a compressor on the sum to let the room pump - watch the release setting - might be the thing you are after.

Niko

If you have some sort of tube distortion plug-in, try just a little distortion or some kind of lo-fi preset if you have one (eq works as well). Then add lots of compression. If you don't want your sound too dirty, mix a clean track with the heavily compressed lo-fi track. Should get you close to what you want. At least that's how I do it and I usually get the sound I was going for.
Cheers

I second pan's suggestion. Put the kit in the garage. Also, check out the free plugin sticky thread in the DAW forum (or is it digital recording?). Download the Blueline collection. The Blue compressor is great colored compression for drums. Also good sources of color found there are Paris EQ and Ruby Tube.

Dirty Drums

I like to get the overall drums mixed into a nice clean, balanced sound, then, depending on the effect (dirtiness) I'm trying to achieve, I'll solo just the kick and snare drum channels and send them through a compressor that's set to squash the hell out of those tracks. Crush the dynamic range and run the comp as hot as you can without too much distortion (a little is nice though depending on the compressor). Then take that squashed drum track and mix it back into your other drums tracks to taste... It'll make them seem bigger and roomier...