Building an LED fixture is MUCH cheaper than buying one, but it takes some serious work... Check out RapidLED.com for DIY kits that come with everything you need. If you want to buy one straight-up, do as much research as possible first. That's a serious hunk of money. You'll be looking for the highest-wattage LED's (usually 1w, 3w, or 5w) you can get for your budget, then make sure the color temperature is correct for your stock (corals/plants/whatever). It gets much more complicated when you start talking about the optics, cuz you have to balance that with the number of LED's to get the right coverage. Some people like the spotlight effect of non-lensed LED's & they put their plants directly in the hotspots, while others will put lenses on theirs & try to get even coverage across the tank/planting area. There's a lot more decisions to make after that, but start there.
