20's are for that BLING factor.
If you plan to go off road, stay with 16's or 17's. It sounds like you want to add rims but use the factory tires. Great idea! Your choice of tires will be greater down the road and rims will be cheaper to replace if you ever have to. By buying the 16's or 17's VS 20's you can get all five rims and a couple of tires for the price diff....
If you aren't going to off road, I think 18's would be a great compromise. Ride quality I bet is better in a 16 or 17 VS a 20" rim and tire combo. Still running the stock set up on ours and will do so until we burn them off on the slick rock.
