First, I agree with Brad. A pair of 6080 pumps would solve all the problems.
However that not being a happening for now, I can only comment on my same size tank. And it was never sps dominated, YET>
I ran a Mak 4 return across one end to the other, a Mak 4 closed loop on the other end and a 3MD closed loop in the center. Plus my scrubber dump. It was decent current but not even close to what my two Tunze pumps generate. Without the closed loops, I experimented with about 6 Hagen 800 powerheads, About the same as the closed loops.
Now although not a match for the streams, I would say it was enough current for a tank, even with sps, as long as the rock was well spaced. In my tank it was just to packed.
I have no experience with the squids, so cant help there. I would think as long as the 4MD, is not losing to much or the Mak4 is not back pressured by the squid, then the current should be fine for now.
Unless of course you have some honkin large sps colonies already. I have read threads where they retard the current big time. My plan, even with the two streams, is to run some 800,s later on when they grow.
I still think its fine for now though and see what happens as the tank progresses.