After many years and lots of wasted money on "better" halogen bulbs, I have to say just go down to your local auto part store and pick up a set of regular 9006 Sylvania or Phillips bulbs. The Phillips are what is in there from the factory (if my memory serves me right). From prior experience, the Sylvania Silverstars at least appear a little brighter and are a little whiter than a stock halogen. However, you make a huge sacrifice when it comes to the life of these bulbs. I have gotten anywhere from 6 months to a year tops (depending on usage) out of them. The piaa's tend to do a bit better on life, but I didn't get much more than a year out of them either (15ish months). Take these numbers with a grain of salt, as I was using both the Silverstars and Piaa's as my low beam (my other car isn't cool enough to come with OEM HIDs). Fortunately, the bulbs on it are super easy to get to, unlike the fogs on the RX. If you are okay with changing the bulbs again in a year, then I would go with the Silverstars or the Piaa's. If you just want to replace the bulbs and be done with it for a few years, then a regular Sylvania or Phillips bulb is the way to go.
Also, amazon is usually pretty fair when it comes to these, though I am not sure how much cheaper you can get than under $20 a pair for a genuine Phillips or Sylvania bulb.