I like the older style rollbars better than the ones on my YJ and the newer TJ. I just think they look better. Other than that, I love everything else - from my lil' 4 cyl to my lack of power steering. I searched long and hard for my YJ just the way it was to suit my needs - stock, pristine, and ready to build!
Just a thought, you said you have about $18k to spend, you could buy and build a heck of a YJ for less than half of that, but you could dump all $18k into it if you wanted to!
The best mod, and if you only do one, this is the one to do for offroading...
Swaybar quick disconnects.