I have a 4channel Jensen Amp it is 400watts, right now I have two subs and 4 speakers hooked into it. But the problem is, the front door speakers their 140 watts max 4-ways and hit really hard when its up on like 10? lol, the way I have my amp now is the one rear and one front is in the same channel then another rear and front in the same channel. The subs are hooked up by themselves and one channel is left. But when the front speakers are hooked up by their self they don't hit so hard, is it safe to hook the rear speakers up with the subs and fronts by themselves?