When it comes to purchasing replacement bulbs, the word "Xenon" virually means nothing. I honestly think the aftermarket world/distributors thinks it's a color. And I've seen the ones you've mentioned on eBay. I'd be willing to bet that those are equal to any other "Xenon" bulbs you can by for $20 or less. Stay away! Many claim to be legal too, which also helps them sell; don't believe it.
If you're only interested in replacing bulbs, I think the
Sylvania SilverStars are noteworthy. They're less yellow than standard halogen lights and truly are legal. They don't compare to a real Xenon lamps (not bulbs) or Litronics, but in my opinion they're the best of the halogens. They should go for under $30 or so (available at any Pep Boys, Advance, AutoZone, etc.).
I purchased an aftermarket HID Lighting System (REAL Xenon) and have yet to install it. Once I do I'll be sure to post my results (w/pictures). Good luck with your purchase and please share the outcome.