I'm tagging along. I have about the same setup and wanting to go led. Google edsreef's DIY LED build. His is only a 90 gallon and is using 48 leds. I'm thinking about going with 2 10"x12" heatsinks and 60 led's but follow how he built his fixture.
Did you want a fixture, If you wanted a fixture and wanted to go cheaper you could most likly get away with two of the 120w fixtures if they are placed right and the rock works right.
Depending on what you are looking to do. If i was building a diy i would build i would say a 36 bulb fixture for each side would do you just fine with 4 drivers dimmable would work i think. If your looking for a fixture at a reasonable price i would check out the evolutions. FOr any more information get at bill at reefled tons of info right there.
I'd say 2x 120 watt evolution fixtures. In the next couple weeks I'll be setting up my tank. 36 x 26 x 26 with 2 120 watt fixtures. as soon as its setup you can come check it out!
I'll be setting a 120 in about 2 months; looking to do the same thing. I'm undecided if it's going to be 2 evolution 120's, 2 of the 150's from Reef Filtration or 2 evolution 200's. The 200's will be a lot of light but I'm also keeping mostly sps. I'll be tagging along to see what you come up with...
Here are the results i picked up with the club meter. I am running two 120 watt evolution fixtures my tank is 48 24 20 both of my fixtures are about 7inches off the water. I have a mixed reef but it is mainly sps as you can see i have seen great growth and color from these lights.
I would go with 4 12" Strip Kits or 120 XR-E LEDs on four 12" heatsinks. Assuming you have a center brace mounting four 12" Kits perpendicular to the back would give you better coverage. With 70 degree optics you would be looking at close to 420 PAR at 24"