You don't have to flash a new kernel but there are many changes that help improve performance/battery life. You can still use an AOSP ROM.
http://forum.xda-developers.com/forumdisplay.php?f=1912
I personally use faux's kernel but I have heard great things about Matrix.
https://play.google.com/store/apps/details?id=ccc71.pmw&hl=en
App I use to UV (thanks to whoever suggested that in this thread)
I really want to try this. But I don't want to lose my game data (I am not rooted yet). Will the rooting remove app data?