Ah, this is my area!! I'm a lighting whore lol.
One thing you need to do is NOT purchase an HID "Kit." They are extremely illegal in all states, so much so that you can be fined up to $250,000 as people have been killed from HID "kit" glare. Join up on the forums over at
www.hidplanet.com.
If you want amazing (non-projector) halogen lighting (Silverstars do suck IMO), do what I did...
-Custom 12 gauge headlight wiring harness with Hella relays - $80 shipped
-Hella E-code H4 conversion headlight housings - $65 shipped
-Osram Hyper White H4 bulbs - $50 shipped
This setup is nearly HID quality output. Driving down the highway or next to my friends HID equipped vehicles, the output is almost identical. If you add some great fogs to it you're golden.
If you need/want to go the projector route, do this... Purchase some cheap eBay housings with completely clear (non-fluted) lenses. Purchase some Bosch, Hella, Mercedes E55 or Audi RS6 projectors. Also, purchase the applicable ballasts, wiring and bulbs. You can then cut the rear of the housing out, retrofit the projectors into the housings, and you're set. This can all be purchased used on the HID Planet forums (or similar forums). You can do an entire, 100% LEGAL, projector HID retrofit kit into your Cherokee for less than $400 (If not less than $200 if you can find them cheaper). This is the way to do it legally and have the best possible output as well.
Hope this helps. If you have more questions, just ask.