I just got a pair of cheap subs to fill in the bottom end of my system, (they're actually not bad for the money), and thought about taking some of the low end duties off my main speaks. I have the subs hooked to the second pair of outputs on my preamp. My pre has a switch which allows one to select between 2 different value coupling caps. I was thinking of using .22uf for the mains and .47uf or larger for the subs. Can anyone forsee any problems with bypassing the switch and hooking both of the caps to the tube output, (it's a tubed pre), and hooking the other end of each cap to the seperate rca outputs? That should give me about 70hz for the mains and about 30hz for the subs.