2 150w or 1 250w HPS?

Hey, im getting a new grow tent that is 2.7x2.7x5.11feet tall and was wondering if i should get two 150w hps's or 1 250 hps? I would also like to know how much a 250w hps costs? If i do choose that, i would want an "air cooled" reflector...not sure about the ballast or anything..so if anyone could give me a rough estimation of what the cost for everything need for a 250w hps. And also, tell me what you think i should buy, the 2 150w or 1 250....the 150's have built in ballasts and no air cooled hoods so im a little worried about heat from them..but i am getting good ventilation..thanks

based on htgsupplys numbers youll get 3,000 more lumens from the one 250w compared to the 150
http://htgsupply.com/Category-250---175---150-Watt-Magnetic-Grow-Light-Systems.asp

250 would be perfect for that area.

Reflector & Ballast - $174.95:
http://www.growlightexpress.com/grow-light-systems-2/sun-system-2-hps-mh-switchable-250-watt-1196.html

250 Watt CMH Bulb - $55.49:
http://www.growlightexpress.com/ceramic-metal-halide-bulbs-9/mastercolor-ceramic-metal-halide-250-watt-87.html

i bought a 150 watt for $70 from bgh and it works great they have great prices and fast shipping

250W:
http://www.bghydro.com/BGH/items.asp?Cc=H2&iTpStatus=0&Tp=&Bc=

150w-250w compact systems:
http://www.bghydro.com/BGH/items.asp?Cc=HC&iTpStatus=0&Tp=&Bc=