If you want to stay with Eheim, look at the Pro 3s. Excellent designs that ease maint.
For easiest to maintain in a canister also look at the Fluval Gs. The G3 would be plenty, G6 might be overkill. Very easy to maintain which means maintaining max flow.
Either way, keep the inflow/outflow simple, almost old school with in/out in same corner, outflow firing side to side.
Read the thread niko posted. In the end, things are simpler than they seem.