Hey Dave,
I am currently in a similar situation, and would like to upgrade my lighting, but trying to do it for as little as possible. I have done tons of shopping around and feel like I have a pretty good grasp on the drawbacks/advantages to each alternative I have found.
For what you want to do with your tank a good set of PC's should be fine, on that same note with the size tank you have it may actually be cheaper in the long run to pay the extra for MH now. I would think that you would want at a minimum of 500W for what you would like to do (that gives you 4w per gallon, which is still fairly low light in terms of photosynthetic corals)
From what I have seen you can get a set of 4X55 PCS (220W) for anywhere from 199 to 400ish, that is for a complete set. So for a premade light fixture for the amount of watts you would need, you would probably be looking at somewhere between 400 - 800.
Other choices would be to do a retrofit, which is basically all the pieces you need, minus the hood, so you would have to do some handy work (I have an .com addy if you want it - not sure if I can post here but they have good prices) A very cool setup would be to do two MH with a supplement of PC doing a retrofit or DIY would be the cheapest way to do this.
Finally you could build a complete PC set, using a Workhorse ballast - I think you would want the Workhorse 7 or 8 - at least two of them to get the amount of wattage necessary. Or a MH set, using a IceCap MH ballast (Im sure there are other brands but these are the two I hear about the most) You should be able to pick up the PC ballasts for under 40 a piece, then you have wiring, endcaps, power cords, reflector, and time costs to consider. Probably be able to get the IceCaps for under 100.
Unfortunately lights are expensive, I think probably one of the most expensive pieces of equipment, but there are cheaper ways of doing things, other then just going to the LFS and flopping down a few hundred dollars.
