[Myka]

In order to cover the 30x30" footprint you need yo use a Lumenarc or Lumenmax reflector with a SE or it will be much dimmer at the edges of the tank. "Traditional" reflectors don't have the ability to spread the light that far. If you want it for SPS, then I would suggest overdriving the SE bulb with an HQI ballast. If you don't mind it being dim on the edges, then your 250w DE bulb should do the trick, you'll just have to either have just sand along the edges or have lower light corals. Is your current ballast an electronic or an HQI?