This is a plug-in but the Cranesong Phoenix can help with fatness and percieved volume. I think it is too much of a blanket to put over a whole mix but what I do is put it on a stereo aux track then send submixes (drums, bass, vox) to it and blend in the amount I want, usually different instantiations with diff. settings for the various groups or tracks I might send to it. If you can get Phoenix only on the bottom end of your mix you might find it helps alot. BTW how are you guys splitting up your frequency bands to process only the bottom of a mix through something and then recombine it with the rest of the mix? Is there a plug-in that works like a crossover, which can send the different bands out for separate processing? I would really like to be able to do this.