RE: New or used ATV and which one?
I just bought the Kawasaki 750i Brute Force for Christmas. Although it came in at @7k, I think it is well worth. You do lose going in some tight places and gain a little weight (600lbs), but the torque and power is unbelievable.
It was nothing to throw on 400lbs of corn, another 250lb rider, and draga deer out. It has so much power it is scary. Alot of incentives and warranties came with it as well.
However, for best used deals, I recommend Ebay. Tons of listings, and alot of guys with buyer's remorse looking to unload newer models.