Best Light for Growing?

What would be the best light for growing in a attic where temp's will be an issue? I'm looking to just purchase one light for flowering, I was looking at the 2x4 4 bulb t5 set up with the 3000k bulbs and would use some cfl's for veg. although I read in a t5 post that they used 3k all the way through I plan on growing in soil space isn't an issue.
Any help would be greatly appreciated.
Thanks

Here's a better option: Buy a 400 watt hps for your flower and use a ventilation fan for your room. Veg under t12s or t8s. You can find t8 ballasts on ebay cheap and just go to walmart and buy a shop light for $9 and switch the ballast. Here's a link to the place where I buy pretty much anything I need.High Tech Garden Supply