yeah you really fear the hps heat until you actually buy one, then its like wtf, i was expecting the sun. They really aren't that bad. My 400 is very easy to cool and i can drop it to almost squishing the plants. I can hold my hand on the glass and it will never burn me. Just get a somewhat cheap little inline fan (dont get the little ones that look like a jet, get ones that look like a turbo) and some simple ducting and your set.
I have done more heat related damage with CFLs than with my hps. all because i bought into the cfls are so cool, the internal ballasts actually add up some significant heat, talking 130+ easy
you would need like 1,000 watts of CFLs in a 2x2x4 space to get it that hot... and your plants would be dead by the time it hit 100, so i really dk what you're talkin about...
but what I would suggest, leeak47, is to look for a cheap air conditioner on craigslist... i got one for $40, 6,000 btu and I don't have to "dump" my heat anywhere. i mean with an aircooled hood the heat has to go somewhere. air conditioners eliminate the problem, but can be expensive if bought new. which is why i suggest craigslist. i mean the inline fan, the ducting and the air cooled hood aren't gonna come cheap. if you live in a dry climate (i wish) you can use an evaporative cooler, too, which is a lot cheaper. but i've heard they don't do anything in humidity. hey, btw, what is the height of your 4x4 room? and why a 250w or 150w? you aren't gonna see much of a difference in yield from the CFLs, especially with the 150w. i use a 400w in a 6'x1.5'x6' (WxDxH) and i would recommend it. i mean your room is certainly big enough (as long as it's not 4' high or something)