like mentioned earlier, do what is best for you.
heres the way I look at it.. pros:
-interior is awesome
-you said you wanted a little more space
-style wise, I think your WK is nicer.
-even though the leather is sick, you gonna want your GSPs on it when theyre older? lol (unless they stay in the trunk)
-the gas mileage is gonna SUCK.
-personally, i think 87K on a 07 is pretty high.
i think the ultimate would be a hemi WK with that brown leather and RER radio. (i know, good luck finding it) haha but do whats best for you.. in risk of pissing the wife off with a 5th car in 4 or 5 years and the fact that you already have a pretty damn nice WK.. i'd stick with it. But thats just me.
good luck with the search/decision. Let us all know how it works out.