I would go with a 400 or if you wanted to do 2 250s, why not just a 600w? Which would be easier to deal with, and be cheaper than buying 2 250watters....and you would get 100 more watts...I can't deal with the heat from a 600w, and i don't really need even the 400w that I have, but they are what I use...and it is awesome, but if you want 2, 250w lights, then I would just go with 1 600w light...
Why the 2 250 split?