I did a test yesterday on 2 different Kicker amps that are Kickers best (if im not mistaken, and by best I mean most powerful)

Real world test vehicle : 1991 Acura Legend 4-DR.
Box : 6.4 cubes @ 33hz. and a swap out port of ~45hz.
Subs : X2 BA Inhuman 12"s
Amps: X2 Kicker XS100's (A/B) (2X150a) vs. X2 Kicker KX1200.1's (D) (2X150a)
Electrical system: 160a alternator, 2 yellows, and a red top under the hood
Test equipment: Classic term lab mic.

Things to be considered: Im pretty much a beginner in the world of SPL so this was pretty basic. Typical Houston weather of 75F and lots of humidity. One set of amps is A/B class and the other set is D-class. I dont have an amp clamp so I cant measure current draw, ect.

I started w/ the XS100's b/c they were already in my car. Both amps are wired to a final 1ohm load to each driver. I played a sine wave from the USACi CD and registered a 151.3 @ 33hz. swapped the ports and let the drivers and amps cool for 5min (nothing was hot, just wanted to be sure it was fair). At ~45 hz. they pulled off a 152.4 (I have hit higher w. the same set-up, but conditions changed?)

With the KX1200.1's hooked up to a final 1ohm load each I ran the sine wave again w/ the 33hz port intact and pulled a 151.9. Then, (after 5 min) with the ~45hz port in 152.9 was the final score of the day.

Verdict : KX1200.1's put up a better score.

More things to consider: The KX series w/o the shroud (gay) makes less of a footprint in the trunk as compared to the long XS series. The XS's have options on the module you put in it (SW equipped) so the results could have varied? I personally like the KX series the best. The XS series id only rated a 100w's @ 4ohms, but due to USACi's new rules the KX and the XS are rated the same.

All tests were done w/ the vehicle at idle......