Get a Peavey / AMR Tube sweetener, and run a mono comp track of the snare and toms ... out of your system in to the sweetener ... and record the output of that back in to your system on to another track. Then mix that track in underneath the original drum tracks (making sure it's in phase).
Better yet: don't. What you're talking about is not going to do what you think, but will add a good dose of noise. If you want a warmer sound, record it warmer. Hint: tube pres have little to do with warmth. Hint 2: start with your heads.
