First question is what happened to the pump? Failed to start, hums, nothing, leaks, smoke? Watermom has the same size pool and the pump is a Hayward Superpump, SP2600X5, 1/2 HP 120Volt. It's an inground model but so what. Baskets are easier to open and clean and they're probably built better that those sold as AG pumps. She's been using it for several years now and the suction and flow are quite sufficient for vacuuming and running her cleaners. She can give you more details on those if needed. The flow rate on that would be a good match for your C900 filter which is rated at 90 GPM. There are a lot of pump problems that are simple fixes and yours may be simple, or not.
Al