I agee with the others that the digitatas are one of the easiest, just make sure you don't let it get out of hand, they can grow very fast.
I've always thought the Geen slimmers were pretty easy to keep.
by no means an SPS expert. However I have had good success, under VHO, with montipora capricornis (sp?). Both the red and green variety. However, the red grew much faster than the green.