There are cheaper options if you only need to drive 2 bulbs, although as Darcy says, the 660 is capable of running 4 of that length.
For a permanent 2 bulb operation, I would suggest the AS-220 (I think that's the name) from hellolights. It's only $35 for the electronic ballast, and can drive 2 bulbs of up to 48" in length. Perfect for what you're looking to do. In fact, if you price it out on their website, you can get the ballast, cord, wiring, endcaps, and URI bulbs for right around $100. IMO, that's the best deal out there for running a pair of 4' VHOs.