Yeah- my comment was meant to come across more as try a frag before a colony from the wild. I have heard of a lot of people keeping sps with vho's. Hard to know for sure on the given setup, and to some extent, the only way to find out is to try- given that the rest of the tank is in good condition, which I imagine it is, as John has had it running for quite some time (I believe as long as my 30- likely longer). I really doubt montiporas will have a problem- acros, I just don't know. Unfortunately, there is no way of identifying "low light" acroporas as we have no idea where they come from in the wild. Most are quite adaptable and will brown up (increase zoox density) if needed, given they can handle the transition to tank life after the whole shipping trauma. Personally I feel the key to determining this is to use a hardier than h*ll acro- some that have made it through h*ll and back- thus they won't RTN/die for reasons other than light. While some in the club have just vho's on their tanks and keep SPS or have had trouble with it, there are only a couple of us with tanks this size- thus comparison on how much light gets distributed to what intensity is difficult. Of course I have a 400W halide, which quite a few people thought was insane to put over a tank this size.
Now one word of caution that may be problematic, is a ton of softies with SPS, but that is another story.