those gavita ballasts are GREAT. the only problem i see is that they are not designed to be air cooled. so you will have to compensate for the extra heat in the room with your cooling system. intake/exhaust fans may not be enough and you may have to get an a/c unit. i think the ballasts on those actually run very cool as well but the heat is exhausted from them into the room too. check around or maybe call them cause i believe the recommend using special bulbs with their ballasts. not sure though, think it mught be a philips bulb. also, think the ballast only runs 240v. not sure if that is an issue for you.
if you can run a 240v line to your room then look at these(
http://www.plantlightinghydroponics.com/lumatek-600w-240v-dimmable-dual-electronic-ballasts-p-2109.html). basically it's a dimmable dual ballast from lumatek. powers 2 bulbs for the price of 1 ballast basically. they only run on 240v though so you would need to bring a 240v outlet (nema-15r) into your room.
you won't need any side lights in veg. vegging plants don't benefit for supplemental lighting like flowering plants do. the whole reason for side lighting is because your overhead lighting does not have the penetration to reach the lower canopy. since you aren't growing 3-4' plants in veg you really don't need any side lighting. i would get a T5HO system and not a T8. T5's come in 2-16 bulbs fixtures. not sure how many plants you are doing but anything from 6-12 bulbs should be just fine. if anything, mix a little bloom spectrum in with your T5's. for example, if you have an 8 bulb fixture, use 5 veg spectrum bulbs and 3 bloom spectrum bulbs. one of these is what you want (
http://www.plantlightinghydroponics.com/quantum-t5-badboy-grow-lights-c-321_952.html). they make cheaper models as well. Sun Blaze, Hydrofarm, etc... all are a little cheaper than the Quantum model. just make sure it is a 4' model and bulbs and not a 2' model.
if you are going to use supplemental CFL's in your flower room then they don't need to be high wattage. make them 40-75w bulbs. also, make them veg spectrum (6500k) as this will give you a broader spectrum in flower which means healthier plants and better yields.