I like Helian 2nd Bass with my POS Peavey's DI track. Gives it a bit of that "Ric growl" even when clean, and the distortion's not too bad on it.
http://www.kvraudio.com/get/1934.html
Izotope's Trash works, but I really like Massey's THC. It's especially awesome in front of Ampeg SVX on DI tracks.
CAMELCRUSHER!!!! I've used that on every bass track since I found the plug. Its free too (upper left corner)
http://www.camelaudio.com/camelcrusher.php