I couldnt help but notice that the MH setup in the original post is running on a magnetic ballast... if funds are limited you may want to concider the long term cost of cutting the bulb life with mag ballast. I'm no expert, so I'm open to correction on this but my research leads me to believe that the elec ballast is the way to go on may levels!!!

I would also seriously concider talking to the dealers (Greg) or checking out hello lighting, with just a little work you could set up a dual MH 250W DIY for around your budget that would blow that fixture away

IMO