You can forget about impedance rise, as long as you are not a competitor or you are not fine tuning an exotic type of enclosure, you just need to have a good working electrical system that is in the level of the amp you are using, good wiring correctly installed, a good amp that does the power it claims, and proper gain settings procedures, it is worth learning about that as well as owning a cheap little scope or a DD-1, if you can source 2K to your subs you will see a big jump in output and you will be pretty satisfied with the results.