Unless you specifically requested a HQI ballast, it's unlikely you got one, and they are significantly more expensive. If yours is a PFO there's a sticker on the top with the a list of ballasts, one of which would be checked off. If it says 250MH it's the M58. BTW, my PFO HQI pulls a maximum of 5.5 amps, a huge draw for a 250W ballast. I'm sure that's only on start up, but you do pay for the HQI buying it and running it.

You really ought to clear up your ballast situation before choosing a bulb. Also, I've heard a 250W mogule bulb will not last a year on a HQI ballast, but I don't really know about that one. Another area that can have real impact on your bulb choice would be reflectors; the luminarc performs so much better than anything else that it's worth getting no matter what, but especially if you like the color of a bulb that has a little less PAR than you want, because it can really get the most out of a bulb. Likewise, a not-so-good reflector like the spider could negate any improvement you might get from switching for the M58 to M80 ballast.

If I had a big tank, I would absolutely be using luminarc reflectors and mogule bulbs; for my little corner tank a DE mini pendant works great.