First, this: "...Well you will have less voltage going to each of the RCA's which will give you less output on the amps..." is incorrect. We're talking voltage - when you run two amps does your power wire from the battery drop to 6volts for each amp. (hint: no)

Second: Don't worry at all about using two similar amps. If you really want, use a DMM to set the output voltage to the woofers but even that is not totally necessary.