i'm doing a 3x3 and going to run 4 175s in luminarc minis. i'd love to be able to do 250s, but can't do the heat or the power draw in the new apartment. but i think it'll work out just fine. using luminarc minis so the spread and overlap from the other bulbs should make up for the lower wattage, plus i'm going to use the new iwasaki aqua2 bulb, which is apparently by the numbers as bright as many good 250w bulbs.
one of the best sps tanks (playfair) on the web is (or at least was the last time i saw of it) a 120 lit by 2 175s + vho.