Hey Mickey, how's it going?
Don't underestimate the reducing effect from having many outlets. I have an AM3k on a closed loop with seven 3/4" outlets and the flow coming out of each outlet is very weak. I guess with the oceansmotions devices, only a few outlets are on at once, but still something to consider. You can always throttle back the pump, or branch off of it to supply flow to something else.
For what it's worth, I just got a used 3600SEQ for a 4 way I plan to get. I may use the AM3K instead and put the sequence on the closed loop, or I may plumb a few extra outlets in addition to the 4 way, but either way, I already have a 5800SEQ as my sump return (basement sump supplying two tanks) and I think Sequence makes great pumps. Also make sure that the pump you got is converted for saltwater. The numbered models need a different seal and a sleeve for the shaft. You can get the kit at plumbingsupply.com for about $40. It's not hard to install.
Vin