Only the Odyssea MH ballast had the problem not the PC's, they would smoke real bad...not catch fire. I wouldn't buy anything from Aquatraders their customer service is horrable if you are one of the lucky ones to have the light arrive in one piece and later on have a problem with the light good luck getting it taken care of without having to give them more money. Also bulbs are not covered under their shipping insurance which is a lie, if they packed the lights right UPS wouldn't have a problem paying a claim. Nothing is free....
As far as your 46 bow, I was going to put MH on mine but decied to go with a Tek T5HO fixture. I have seen the center brace melt from a single MH over the center, it happened to my 65 gal tank and the bulb was 8" above it. I like T5's better on my 46 less heat, I keep SPS, LPS and softies under the T5's. If you want MH's I'd recommend going with 2 bulbs so it's not over the brace.