How fast is fast in growth for SPS?

[Aquattro]

I find it's really species dependant. My old tank had Marie style growth, one piece put on about 4 inches on each branch in 2 months. Other pieces I had grew an inch in 6 months.
Besides lighting, make sure you have strong flow (although not direct flow on coral), and great water quality. This means proper alk, Ca and some people measure Mg as well. Mg has just been a recent concern in the last few years, so I couldn't tell you what my levels were when I had my "steroid tank". I do know I had to throw frags in the garden because I couldn't give enough away.