return pump suggestions??

[christyf5]

Just looking at return pumps here.

So I'm going to be upgrading to a 180gal hopefully within the next 6 months (fingers crossed). I've got 2 3/4" sea swirls that I'd like to use on the return and they're rated for 850gph each. So ideally that would be 1700gph total. The return line will be nothing special, either PVC or that flex stuff. So it will come off the pump, then tee off to the two sea swirls. Likely about 8ft from pump to sea swirl.

I was looking at the sequence Dart but the outlet on those is 2" and I can't imagine having to go from 2" pipe down to 3/4". Then I was looking at Chin's Iwaki pump (70RLT) but at 8 feet it only gives about 1200gph. The tank will also have a wavebox, 2 tunze 6060s and a tunze 6045. I have never been able to figure out turnover rate as I always thought it was just about the return pump but people seem to include anything that moves water in their calculations. Does a larger tank need more flow through the sump?? Currently mine is so stuffed with equipment I often wonder if there is even any flow in there For the new tank, I'm hoping for about 50gal of water in some sort of sump tank haven't decided on what form that will take yet.

Frankly I don't really know what other pumps are out there. I've always used Mag drives as I have no room for external pumps and everyone sells them and various replacement parts.

Soo.....suggestions?