*D3nb3r: you can use your ears for level matching. for stereo, test tone is used to adjust the balance (or gain/level) between left and right channels. actually, you can even do it on-the-fly while listening to music.

test tone of different frequency can be used for determining frequency response of each driver (bass, mid-bass, tweeter) or testing the crossover/filters. it really depends on what you want to accomplish.

basic question, have you read the user manuals of Rockford Fosgate p300.2 and Polk Audio MMC6500 Momo already? you can download both online. they are very simple to connect and setup. i think you worry too much.

how to adjust the gain of Fosgate p300.2

ADJUSTING GAIN
To adjust the gain setting, turn the amplifier gains all the way down (counterclockwise). Turn the source unit volume up until distortion is audible and then turn it down a bit until the distortion is inaudible.This will be about all the way up on most source units. Next, increase the amplifier gain setting until adequate volume is achieved.

NOTE:Best signal to noise and dynamic range are realized with the gain at minimum. Most users find adequate gain and volume is achieved at about halfway in the adjustment range.