I ended up going with a 4 bulb, 4 foot, High Output T5 system that I got on sale from the Hydroponic store. I did this partly because of the higher lumen per watt rating but also I needed something fairly compact. I would have needed many more T8 bulbs to get the same amount of light.

T5 is still kind of expensive, I would guess T8 would be the better way to go if space is not an issue.

I have seen 4 foot T5's at a big box store, but they are not High Output.