the Quantum
the Quantum is an awesome water vac, costs $500 in the United States and cleans every bit as well as water vacs costing 4 or 5 times that price, and it actually does one thing better than the Rainbow. With the current model Rainbow, when you fill up to the center post, the separator is not actually in the water so there is a gap before what you vacuum up hits the water. The Quantum actually holds more water and the vacuumed debris goes directly in to the water because the separator is always in contact with the water. Don't get me wrong, I like my Rainbow but Rexair could learn from the designs of some of the other water machines.
Mike