Sub hookup in a 2ch/HT system with preamp passthru

Can anyone tell me the best way to hook up a Velodyne DD-12 to my system that uses the preamp (Mcintosh C2200)for 2 channel control and also as a passthru for my processor when listening to HT/satellite. The sub has 1 XLR input and 2 RCA inputs. Do I need to run cables from both the processor and the preamp to the sub? Can I run just one pair off the preamp outputs into the sub and that will work in both 2 channel and when the preamp is passed through? The C2200 has 3 sets of outputs. ANy help is appreciated. In speaking with Velodyne (who thought I was a minority using a preamp as a passthru for HT) they were no help what so ever. He told me the sub was meant for just one input from EITHER a receiver, processor, or preamp and that adding other components to input would sum all the signals and degrade the performance. THanks again. Dave