I am planing on a 36'' L and 24'' H tank. I will get 2 150W DE pendant. Do you guys think I can keep most SPS with this setup. I was think of 250W DE but I think they will give off too much heat for 36'' tank.
You can keep most SPS with dual 150W but I would err on the side of caution on higher light loving SPS because of the depth. 2 x 250W or 1 x 400W with the right reflector (Luminarc) would do also if you are serious about keeping any and all types of SPS. But in most cases 2 x 150W HQI's will do as well.
By the way, dual 150W HQI's will give off almost the same amount of heat as 250 watters. Only difference is the electric bill every month. You also should say if you are going to be using any supplemental lighting in your setup for a better answer.