it's pushing a little bit more water into my 200G than my overflows can handle.
I know a guy using the AMP 300 on his 120G with Dual overflow. In situation like yours, you can do several things:
1) Mess around with your Durso pipe some more. Different holes size drilled into the cap determine the flow capicity of the Durso Pipe. Place your fingers over the hole in the cap of the Durso. Is your pump still not keeping up even when the top hole in the Durso have been plug up?
2) Surface Tension could be your problem if the overflow box can't suck in enough water. In that case, it's up to you to decide whether or not to widen the teeth on the overflow box. In my overflow box, the surface tension get about half way bwtn the teeth b4 it would drain into the overflow. The guy I know have this same problem in his 120G, but he's not keeping the grilled slot clean from algae buildup.
3) Drain some excess flow back to the sump through a ball valve if your overflow can't keep up with your pump.
Look at all those live rocks on the beach at Florida's state park!