I think it really depends on you, your size and what you want out of the sled.
I'm currently running an X3 on a Pro 163, some handling mods include an Alternative Impact narrow front end, Ice Age Pro-Motion, Raptor shocks and SLP skis. For me, this combo works great!!!
I'm 6 foot and about 240 and have not problem whipping the sled around or laying it on it's side. The sled flat out works.....for me. I'm not a big jumper and wanted somthing for wiggling through the trees and something to hold an awesome sidehill, mission acomplished!! If I was a little smaller, I would have tried a 155"
The three in track is pretty damn cool, but the next track I'll be trying will be the new 2.6.
Good luck!!