Well, I have a EV150, Aqua-C suggests Rio2100. The closest to Rio2100 is Mag-7. I tried Mag 7, and didn't like it. Then I tried Mag 9.5 which is rated 950GPH at 0 head, and is working VERY WELL!!
My Mag9.5 is great for my EV150, I would imagin if you have the EV200, you would want to go atleast the same size pump as mine or bigger!
HTH