I have an '02 Suzuki Eiger 4x4 and I absolutely love it....I have put that quad through so much and it has never given me any problems. It is plenty fast enough for me, the 400cc has a good pep when you hit the throttle, and it loves to slide! I have gotten it stuck twice but if you could have seen what I attempted to do you would understand...It climbs very well on steep terrain when in 4wd low, it has a speedo etc also... I don't know what the Eiger runs now but I got mine when they first came out and I paid about $4900 for it. I plan to upgrade my tires, maybe to a 26, then a winch and maybe an aftermarket exhaust if one is made for it....

 

Honda Foreman 450 ES.
Selectible 2-4 wheel drive, Super Low first gear, tons of torque, Honda reliability, built like a small tank and goes most anywhere the big boys go. I have seen amazing things out of these ATV's in the
mud-pits. As long as ground clearance is not a big issue only 7.7" you can't beat the ForeMan!!
OH YEAH you can pick one up for around $5200.