+1 on the GSP and Xenias!
I hate Xenias! GSP are nice, but grow too much. Now, if you have a large sandbed you can have both of them. But make sure neither will get near a rock else they jump that sand bed and take the place over!
The sandbed is a great place to banish bad corals...Keeps them from spreading.
Too bad chalice and Acropora dont grow like Xenias!