I've done some research, now I'm seeking experienced consultations /
opinions.

My current growroom is 54" long, 30" deep, and 68" tall for a total of 76.5
cubic feet. I have an exhaust fan rated at 70cfm installed in the ceiling
and an air intake at ground level.

I'm currently lighting with a dozen cfls at mixed wattages from 27-42 watts
each and seem to be doing pretty well. It's just irritating having to raise
the lights on a daily basis to keep the leaves from grabbing hold of 'em.

I want to switch to a mh/hps system and found a 400 watt switchable
system here: Grow Light Kit- 400W HPS MH Digital Ballast, Full Spectrum Bulb, Reflector

(sorry if the link stretches the screen)

My current temps in the room stay at around 76degrees f at plant level,
and never rises more than a degree or two max recorded temp.
Humidity stays at 30-40.

Will this be the way to go or am I aiming low to keep my lighting system
under US$200.00?

Will I need additional cooling? I know I've got about 8 or 10 degrees to
play with before I've gone over the maximum recommended temp.

Thanks in advance guys.