I have Silverstar's in my Bronco II, Silverstar Ultras in my dad's Dodge Dakota (also 9007 Bulb) and there's not much difference between the two (we installed them at the same time) so I wouldn't say the Ultras are worth the $10 over the normal silverstars. They are MUCH better than a standard halogen bulb though, a lot whiter, and significantly brighter. They come close to the 4000k that they claim.
That said, Phillips xtreme are the way to go. Brightest bulb out there that you can get really. The Ultras are ok though if you want to buy locally and don't want to mess around buying stuff on the net. I will say though, that once my silverstars burn out, my headlights are getting Phillips bulbs.
Hope this helps!