I converted my dim halogens for a HID kit bought on ebaY for about $200 about ... 15 months ago. My kit has HID lo and halogen hi. They are excellent. 15 months later they still kick a$$!
It took me about 1/2 hour to install them...max. They use the same plug as the halogens. I mounted the ballasts on one of the screws right next to the headlights. Literally "plug-n-play" with nothing to cut.
My 930 Cabriolet has the same kit and they are awesome!
Search ebaY for "HID hi lo 9007 kit"
My brother converted his halogens in his 07 FJ Cruiser to a new breed of HID kits. His bulbs come with an actuator that tilts the angle for hi beams - yeah, pretty cool. He also bought them on ebaY for less then $180.
Try this ebaY seller: flashplus
http://motors.search.ebay.com/_W0QQsassZflashplus
Forget PIAA or Hela or Sylvania or anything else and pay upward of $500+. All the parts used in those kits are probably from the same manufacturer but marked differently.