FIRE UP is exactly right except a Jeep Rubicon IS the most capable stock off roader you can buy today. I see you were talking about a Sport. It is very capable off road as is the entire Wrangler line up. Most Jeep rentals in Colorado are going to be a Sport, so you know for moderate 4 wheeling, they are capable. In 4-lo, they are all pretty close to the same anyway.
As far as tires, most comments are right on the money. I had the BFG Mud Terrains and hated them on my Rubi. When I upgraded, I went with LT35x12.50 17s. HUGE tire. There are some that run 37 and 40s. IF YOU DO NOT DO EXTREME 4 WHEELING, just buy slightly over-sized metric sized tires that are siped that will provide good overall performance. The 305 to 315 sizes are nice looking, require minimal to zero lift, and will be less noisy than mine.
I consider myself an above average guy when it comes to wheelin and the way I set my Jeep up tackles 99% of the trails I go on. They are noisy, get lousy gas mileage, and are expensive. But they will tackle Moab and Ouray with ease AND tow behind my MH with zero issues.
2013 Discovery 40G, 2012 JK Rubicon TOAD1, 2014 Grand Cherokee TOAD2. 2013 RAM 1500 Longhorn. American Steel = American PROFITS!