optimal flow rate

[scsi]

I'v been thinking about flow rates on my 77G tank. Right now I have 2 Seio 620's and 2 MJ 400's circulating the water. There is also a Fluval 405 which is only used for mechanical filtration and carbon. I guess that gives me 2040 GPH. Is this adequate for a tank this size? This is assuming that I will eventually want a few SPS in there.
I'm not happy about a few dead spots I can already see in my tank. There's nothing in there except for the LR and a Sea Hare. What I think would work really well is a powerhead that has an automatic 180 degree rotation back and forth. A couple of good sized units like this placed at either ends of the tank would be perfect I think.
Would a Hydor Koralia 3 do something like this?