I have had luck to ride a 350 4t, 500 4t and a 300 2t with various kits during a demo with Adam Yantha. Big boar is great as Zedro indicated. The 250 may be a little under powered (no offense but, you will be on the pipe a ton!) The 500 was great! (Not because I own one!)
Shorter track length for our riding (Ontario) area is better (IMO) as the long track is noticeably difficult to turn on shallow or hard snow pack. The Timbersled vs. Yeti... I would buy the Timbersled.
The kits really come to life in 12" of untouched snow.
Give some thought to calling around to various dealers to get some feedback on your bike with a kit is my suggestion to you!
C