IMO if you are looking to upgrade...a 600W hps would be the easiest and most efficient to manage in your prodjected new grow space. If you went with 1000W, hps or LED, you would in all likelihood need a/c to control temperature but if you limit it to 600W you can most likely get by with only a strong exhaust system and good circulation fans. Again, IMO a 4x4x80 grow space will be far easier to manage than the smaller space that you are currently working in. My estimate is that you are currently drawing 425W total from your 3 lights so you would be looking at a 175W increase in power draw if you upgraded, independent of any increases in draw created by upgrading your exhaust and circulation needs.