ok i have an older JVC Headunit with 1 pre amp. I want to run my two front speakers off of an amp with 2 subs running off a seperate amp. if the head unit is only putting out 1 pre amp output would i still just run that to the newer sub amp, then run an extra RCA from that amp to the front speaker amp? i know how to hook all the power wires and ground i just dont now if the 1 set of preamps would hurt it since i would be running front AND rear through that. i could buy another HU but i do not have the money as of right now.
It won't hurt, and yes, you'll have to run the RCA's either from the front amp to the subs or vice versa. The big thing is you won't be able to fade out the sub level, so it will have to be set from the gain of the amp rather than the head unit. You can do that for now and if you're not totally happy setting gain, you can buy a new head unit when you have more $$.