I put most of the Kicker system in my 12 GT. I used these as my main speakers (Infinity Reference 6832cf 6 x 8/5 x 7-Inch, 180-Watt High Performance Two-Way Loudspeaker). Everything else was the Kicker system.
The only problem I have with it is that there is no way to adjust the sub. If you have some bass heavy music you'll kave to turn down the bass from the HU.