If you want to process external sounds, I would recommend an input module that includes an envelope follower (so that the incoming sound also produces a control voltage that triggers other things in the system). Doepfer makes an inexpensive one, but I didn't care for that one, so I use a Future Sound Systems TG5 which is killer. I do love the Doepfer spring reverb though. In fact, I recently weighed the pros and cons of the Erica, Intellijel, and Doepfer spring reverbs, and decided that the Doepfer was the best option for me. Finally, you may want to check out the Soma Lyra FX module for deep, dark delays. Seems like it might be valuable for the sounds you are trying to make.
Have fun and good luck.
-- farkas
Checkt out the TG5, looks realy interesting but don't know if i am willing to pay that price for an input....now. Will put it aside as a possible future purchase....