Need new lights help

Have a price limit? Because if you can afford the better/brighter lights, cooling, and monthly bills I don't see why you wouldn't just get the 1000 watt system with a nice 8" inline fan.

 

$130 for a 400 watt system although I'd spend the extra $15 for the 600 watt version, both have a MH and HPS bulb (but you'll pay $20 more for a cool tube setup, which I personally like to help with temps a lot). 6" inline fans are about $70-80 which sets you about $200. Ducting will add another $10-20 at your local hardware store or online.

 

For ventilation I use a single fan to pull air out of my grow area, which for you would be the 4'x3'x4' area. The space inside is going to heat up a lot with that light, so it's good to pull out hot air (either from the cool tube, or if you don't use one from the top of the grow area where heat has risen). You want to create a negative pressure with the fan pulling hot air out, essentially bringing cool air in passively (and usually from low down, like the ground).
 
Not using a cool tube is fine and without the glass is actually more beneficial (with the metal halide bulb, usually used during veg) as far as not blocking out UVB. However your bulb (400 or 600) will be really hot and has to be kept farther away from the plants. To help combat this you should be using a circulation fan inside the grow area. I recommend any setup to use circulation fans, but even more so when it's a smaller space with an open bulb.
 
I just took a temp reading off of my 400 watt bulb inside a cool tube and it read about 145 degrees F. But I can put my hand on the glass without issue because the cool tube is really quite effective. My plants at canopy level are at 75-77 degrees F and the cool tube is only 6 inches away (so maybe 10 from the bulb itself). I'm not sure how much more heat a bulb will put off without the cool tube just sitting there, but it'll more easily fill your grow space up with hot air.