CFL to MH/HPS?

OK, I'm vegging three plants with about 500W of CFLs right now... I have been contemplating a 400W MH light... what I am wondering is, if I can only fit one light that size...? Should I get an HPS instead, and if so what color temp is best to get, or should I get two different color bulbs for veg and flowering?

I have a 400watt with MH conversion bulb and HPS bulb with ballast and hood for 164 from High Tech Garden Supply

Its best to use MH for veg it makes alot thicker plant IMO and then switch to hps for flower.