If you're on a budget, you may consider just using 4ft T12/T8 shop light fixtures. I use two of these fixtures for my 75g. I found some nice flat ones at either Lowes or Home Depot. I got the bulbs there too. I use a combination of the full spectrum (2) and plant growth (2) bulbs. Definitely less than $100 for everything.
This has worked great for me. I added DIY CO2 and now I kick back and watch the plants grow!
http://s24.photobucket.com/albums/c3...lantGrowth.swf