Hey junkyard, you should look into just getting a hortilux bulb for your HPS and forget the mh all together. The hortilux offers enough light in the bluer spectrum to keep the plants from stretching, and you'll save money. You should check out www.hydrowholesale.com (i ordered my 1kw hps from them on a friday, got it that next tuesday)they have good deals on cool tube lights, which is what you should be more worried about. Get an air cooled hood, you will not have heat problems and can keep your light close enough to your plants to max out your yeild.
http://www.hydrowholesale.com/Mercha...gory_Code=BAIR

And if you just want the cool tube itself and not the light/ballast, you can get the cool tube for 59 dollars here(it says like 119, but add it to your cart, its on sale):
http://www.marylandhydroponics.com/ht-reflectors.html

If you want to see the results of vegging with CFLs for a bit then vegging and flowering with hortilux superHPS, check out my grow in my sig. Imo, you'd be better off with a cool tube than a switchable ballast, and the hortilux bulbs rule.