There is a website that tells you how to build a single halide set up for $100.00. You would need 2 though and probably some sort of actnic lighting. I am researching the same thing for my 75 gal
Check ebay. There is a 2x250 with 2x55(or 2x110) VHO
retro kit that you can get for about $430 shipped including bulbs. Couple of sponsors have the coralvue setup with a 2x250 and T5 actnics for $510-520. The coralvue has electronic ballasts too.
Unless you really want to build it, these are the best I have found. These will require you to build a canopy too.