Need some help with exhaust???

Im gonna be makeing a trip to Htg supply tommrow and ive been haveing issues keepin my temp down in my Grow cabinet as of right now ive got 2 6inch duct booster fans one exhaust and one intake also ive got 2 4 inch duct booster fans one intake and one exhaust. i cant seem to get the temps to stay lower than 88 to 92 so i was thinking of just gettin a blower but ive never used one before basically are they a better way to exhaust than what i got. The cabinet is 48x20x72 any help would be great thanks. This is the blower i was thinkng of gettin or should i got up the the 465cfm blower i would love for it to be over kill?

http://www.htgsupply.com/viewproduct.asp?productID=52492
http://www.htgsupply.com/viewproduct.asp?productID=52505

whats your setup like?

Oh my bad im useing cfl for lighting i have 8 26w 6500k and 3 68w2500k

Well i went with the 465cfm blower and now it is the only fan running my cabinet i have 2 passive intakes now and the temps have droped 11 degrees.. Its holding a steady 78 in there