tuning amp to subs

how is everyone doing? im new, my name is jason. im from columbus ga. i run a stereo shop here. but to the point i guess. i installed a system in my honda about a week ago. and have some questions.

the amp is a kole qx13000d, 3000 watts max.  rms is 2300 @ 1 ohm.

the speakers are splw12, they are dual 1 ohm, rms is 1100 @ 1 ohm.                                                                

the box is a vented box, the port is like the kicker box, 1.74 cu.ft per chamber the subs call for 2.4 per chamber. ive got to build a box to get the right cu, ft. but thats not my issue. after installing every thing, and playing with it, it seems like the subs are under powered. i looked online to see the best way to tune everything. i found something, that said to turn all filters off and all other settings to 0, then on the sub amp turn the gain to 0. then unhook the subs and hook a multimeter to it, and play the 60 hz bass tester cd that i burned, and then from the chart off line turn the gain up till the meter reads the same volts as from the chart, that match my amp and subs. i hope this makes since.

Doing it by ear is fine.  Indeed, I usually use a volt meter to set a starting place and then use test tones to listen for clipping as a fine-tuning step. It is not just high-dollar systems that need set up properly; indeed, I'd suggest lower-end systems are much more prone to clipping than are higher-end amplifiers and setting the gain properly is much more important when using cheaper amplifiers if you don't want to blow your speakers.

But back to you situation.  As long as the amplifier is setup to match the head unit output, that's the best it can do.  If you don't think the subs are performing properly, it's the enclosure.