I have the small one on a heavy stocked 250+ TWV system and it rocks. I will say one thing, they are under rated ffor what they can handle.
And Dave will down right hook you up for customer service aand "mods" to a point. I have the small one and have the medium cup on it. I even have the medium pump i can put on it. These things are built like a tank with really thick acrilic and reallly easy to clean.
If you get it you will not be sorry!