Well, if you wanted to do a closed loop, you could do so. This would eliminate the need for as many power heads in the tank. All you would see is locline returns for the most part...and the strainers over the intakes.
On an old system I had a closed loop with an Oceans Motions 4 way and a Reeflo Barracuda. It was pretty excellent.
can you fit both the 35 and 45 under the stand? If so, you could connect them with maybe some 2" pvc
and bulkheads, and make that your sump with refugium if you liked.
You could split one or both of them to accommodate whatever you wanted.