You may want to check the Tires, Wheels & Brakes section of this forum. Do a search, research what you are looking for - road, trail, rock-crawling, mud. I would assume that you could spend anywhere between $100 and $200+ per tire depending on what you want to spend and what you want to do.
I did some research on this forum and chose to go with the Revos for my 2001 and they are getting installed as I type. Cost was about $120 per tire plus about $55 for shipping from TireRack.com, and I'm having them installed locally for about $50.
_________________________
Steve