Thanks Dave. I'll always use a separate pump for the spa jets, so the existing 2 horse (or a direct replacement) should be okay for the spa. I read something relating hp requirements to number of jets - in this case I have 6 (it's a nice roomy spa).

I will get out the pencil and paper and the Ultra Flow charts and figure out what my requirements are for the main filter circuit. I suspect that 1 hp single speed is right (i.e., Sylvan sized it correctly). What I want to figure out is if the Ultra Flow pump can work with the lower RPM of a two-speed motor, and if so, what size motor will give best results for regular filtration at the lower speed.