Go with the MW and the HPS plan. Or, if money is a factor, just use cheap CFLs for veg, and HPS for bloom, and forget swapping bulbs on the ballast. That way you can have stuff vegging while you have other stuff flowering.

And those big Envirolights and other large CFLs do generate a fair amount of heat. If you touch them, they don't feel incredibly hot (compared to an HPS bulb) but that's partly because A) the CFLs don't put out nearly as much light; and B) those gigantic CFL bulbs have a much larger surface area from which to radiate their heat. When you confine them in a small space, you will see that the amount of heat they generate is far from negligible.

I believe the 200 watt envirolites radiate around 20k lumens, and they do consume 200 watts. So three of those would just barely exceed the light generation of one 400 watt Hortilux bulb, and it'd probably take four or five of them to equal a decent 600 watt bulb. Consider your bulb costs here too. Does it cost a more to replace four or five 200 watt envirolights than it does to replace one 600 watt HPS bulb? Heh, yes it does, by a lot.

Just get some 6500k el cheapo CFLs for veg; they work just fine, they're cheap, they're easy to get just about anywhere, and they're not inordinately huge. And get a 600 watt HPS ballast for your flowering. If you have the money, get it with a cooltube with an internal reflector, and with a digital ballast. I think this is probably the most efficient, effective and cost-conscious route for ya.