Ditch the sump, and stick with two power filters, and a canister. If you didn't realize you were going to have issues with the canister and sump being on the same level, then it might be best just to avoid the sump. The canister most definitely is going to have difficulty pulling water from the sump seeing as how canister filter intake works off a siphon. Here's a suggestion, (I'm assuming you are going to go with a 60-100 gallon set up) if you want some nice filtration for your discus, go with two high output customizable filters 2 AC100's, and one large canister filter Fluval 404, Rena Xp3 etc.. That should satisfy your needs.