there was a post earlier that discussed that so you might check it out....i also would advise to checking into some amps that have a 3 channel ability.....some amps are designed specifically for what your wanting to do....
ur best bet would be to run a 4 channel amp or a 3 channel amp. ur speakers should get their own channels and ur 2 subs can share a channel, or get their own if u want. a 2 channel would work, but is not usually recommended.