IME it is always better to just buy kick-*** lights the first time around. I too am going to undertake a LED project, but i hear they are harder to get a hold of overseas. In which case, I would go for a T5 setup. Some other things you may consider, are you ever planning on upgrading tanks? Will you ever venture into SPS, clams, or higher level coral?
For me, it always seemed like I bought a 24" fixture for lower light, then wanted a 36" sps frag tank or something. I really thing DIY is the way to go, you put it together, you know how it works, and if you ever need to, you can strip it and retro it into something bigger or better. Maybe if you are planning on upgrading in a year, you can buy a 36"er and scoot the legs in to fit on your current.
JM.02 I wish someone had made me look ahead, i have like 4 fixtures laying around that i really dont have much use for.