Welcome to the forums!
If ground clearance is not a factor then go with a buggy. Your equipment chioces sound good, but go for 5s lipo and gear the 9xl down. It will run cooler and you will get better run times. If you want to stick with 4s go with an 8xl. This is assuming you are going to use the buggy. The 1/8 buggies are lighter and have less rotating mass than a truggy, so they are easier on the motor. Geared for 35 will also keep the temps down and the runtimes good. Not sure if you have seen briang's speed calculator, but it is a great help in setup choices:
http://scriptasylum.com/rc_speed/_top_speed.html