We are looking also, and we are considering the WJ and the BMW X5. We currently have 2 XJs and 1 ZJ.
I think that either of them would be a nice option. We have found the WJs, a couple years old for about $15-18xxx and the X5 in the $25-29xxx range. We are looking at 2 or 3 year old vehicles with less than 45,xxx miles on it.
In regards to some of the other vehicles listed, the Murano and the Xterra were the only 2 I have any extended experience with as I worked at the Nissan Plant in TN.
The Murano to me feels like it is smaller than the KJ. I don't know if it really is, but it feels like it is when I drive them. I felt like I needed to hunch down to get the head room I feel comfortable with. The Xterra is alright for the space and such, but when you get to running around in them, they are rough riders. They are definatly more "truckish" than the WJ or the KJ.
I did rent a new WK in June for a couple hundred miles and liked it fine. Not long enough rental to get a huge feeling for it. I did also rent a KJ for a trip to Washington DC from Nashville. We put well over 1500 miles on it and we really liked it. The only problem I had was that I am 6'6" and the bar on the dashboard over the glove box kind of impeded on my leg/knee space.
I think you will be happy with a WJ. I think that between the WJ and the X5, the WJ is much more feasible due to it's cost, as well as it being easier to work on. I opened the hood and the X5 and barely recognized anything! It is all covered with plastic and shiny stuff.
Good luck with your purchase, and if you get the WJ, let us all know your opinions on it after your "break in" period!