Oh, and as for your question...I've heard of people providing the right temps with just an infrared bulb, and they haven't had any problems. I myself prefer UTH, as the belly heat helps for digestion. I guess it all depends on what you're more comfortable with. I'd still use an UTH...I mean, if you just use a bulb for your heat, you should make sure you have a spare incase it bursts or something. With a UTH though, I assume you'd get more usage out of it. Plus the temp gradient thing. Not too sure how well you can get a temp gradient with just using overhead heating.

So, in short, it's up to you. If you can maintain the correct floor and ambient temps with just a bulb, then go for it I guess.