I have the Vision X XMitter Series 42 inch that I paid 1600 for. I don't know where to find either one cheaper. But let me tell you, they are bright. I kinda want to see one of the Holder ones (now known as Rigid Industries' Edge Series) to compare it to mine.
As to custom building one, I am currently making a six inch one similar to my purchased one that I will be using the Seoul Semiconductors P7 emitter on. My post is on the Automotive list somewhere. When I get some money to throw down on 8 of the P7's and a few buckpucks, I'll finish it up and post pics of it and its beam shots. I already have a reflector plate made and I just made up a prototype design for the Base/Heatsink today on MasterCam. I'm not going to make it until I get all the components for it, but I thought I should have some sort of an idea for it. Vision X just made a 6 inch round light with 6 10 watt LEDs (I would imagine they are a ssc p7 or maybe an MCE) and a 4 inch square light that both put out a ton of light. I'm hoping my custom built one works as good and is as bright as these.
Trevor