You really need about 1300 -1400 GPH in water movement for your corals. Hydor makes affordable, good power heads. Try buying them from Amazon, they usu sally have really good deals on them! I got a 1400 for $24.99 early last year. Should have bought every one they had at that price.
As far as placement, well if it were MY tank.......and I'm not an expert at ANYTHING...... I would put a 750 stage right, High, facing left. Your 180, stage center pointing at the surface and another 750, stage left facing right a little lower that the one on the opposite side. Both outside ones pointing to wards the center with currents crossing at the lower side of the center of the water column. Make any sense?
750................................180...............................750
...........center of water column..................................
..........................aim here.......and here....................
.......................bottom of tank..................................
