Im also starting my sled research...
I live in summit county, CO (9,000feet and higher), weigh about 160 lbs., and a total beginner.  My price riange is hopefully $2500-3000.  I have a few sledhead buddies who gave me these recomendations:
Polaris RMK 700 144 track or longer - good cheap, reliable sled
Ski Doo Summit 700
Yamaha Mtn Maxx 700 - 144 track or longer
That being said, i think Im going to search out a 700 rmk first, , i guess theyll have good enough power for me, and be reliable, unlike the 800s and 900s.
I will be using my sled and first a tool to go skiing, second, a toy.
So maybe there's a few tips for you, depending on your price range.