IMO MH lighting is only necessary if your planning to do
sps corals and clams. Most, if not all, other corals do fine under
PC lighting. Even some
sps corals do well under
PC lighting. You also have to take into consideration depth, not just
wpg, when thinking about what lights to have. If it's a deep tank,
MH's are gonna penetrate better but a shallow tank,
PC work fine.