I was running a 400 in an area about that size in my basement for quite a while. Over the summer temps got a bit high, peeking into the 90's even with an 8 inch exhaust tube and inline fan (ghetto rig household booster fan in a cardboard tube with the inside painted black to block light)

I got the glass for the hood (Sunsystems-2 all in one deal) and pulled the heat from the bulb into the exhaust, dropped the temps into the mid to upper 70's!

The 250 wont properly light that whole area, but it should do nicely over 1-2 smaller plants. specially with the t-5's as side lighting.