I've got the AT1500 from Accessible Systems, what I really love about it is the clamp system on the "T" bars that allow for infinite adjustment to get the car exactly balanced. I can spin the car easily and its extremely stable. I also vote for the water blasting (you gotta have HOT steam)to clean the undercoating. Check out the before and after photos, this one had very thick undercoating. It took about 6 hours to get it this clean.Notice the original dip primer visible on this 33K mile Hamtramck car.I didn't even have to use any media to clean this one but I always use "black beauty" (coal slag)when I need to blast but it's way too aggressive for the outside.

http://www.accessiblesystems.com/bul/15/15.php