By far the best are the p5b deluxe and the gigabyte p965 ds3.
The xbx or "badaxe" is a pretty decent overclocker too though
The e6600 and above (conroes) overclock well on it. E6400 and 6300 (allendales)....not so well.
Go into the bios, and start oc'ing, it should still give you a nice 400 mhz fsb minimum, which would be easily enough for 2.8ghz on your e6400.