I would go with the 4 250's. I did a quick price check and its a little cheaper to replace 4 250 bulbs, than 3 400's. I think its icecap that sells a pendant that can be used for both. Of course your ballasts won't, but if you decided to upgrade to 400's, you'd be a step ahead.
I would use 3- 250 watt halides- it is more than enough, plus you will save on electricity and excess heat. Use good, high end reflectors and you will have full coverage with no dark areas in the tank. If you can fit them, I would look at Lumenmax Elite or Lumenbrights if you have a high canopy. I use LumenMax 2's on my 120, and they give very good coverage.