Hell yeah dude, I'm about to load another 400w in my 4x4 to accommodate the growing girls, so a total of 800w in there. I really just need to buy a 1kw fixture, but that'll have to wait, I just bought a ozone generator for my air intake to keep my room mold free! Woot! I saw a purple sour d clone the other day, I really wanted to take it home but I'm already putting clones to veg in my extra 4x4 that is supposed to be a 600w experimental tent at all times, so I really don't have the room. Oh man, have you seen the new 750w ballast by hydrofarm and herculese? I think I'm going to put one of those in each 4x4 instead of 1kw or 600w.
On your level I suggest co2, but co2 isn't as effective in a tent. The local dro shop has a co2 burner for 200 bucks on a open box deal, think it'd be worth your money to ship it out to you? I think they have some stellar deals on regulators and monitors too. They have garage sale prices on their open box/returns.