If you are on a budget, I feel used equipment is the way to go. I am a DIY guy all the way, but I wanted a nice metal enclosure so I bought a real nice used dual-MH setup for cheap. Been 6 months and its best thing I ever did.
Not to mention wiring up a DIY MH which is to be installed over salt spray can be a bit unnerving... I feel it should be done well.