I dunno. Granted, My fx rear/cargo is a bit tighter than most suv's, but it's only because of the sexy roofline/ass it has. The ride is reaaally stiff with the sport susp. and 20's tho. Rocky trails might shake up ur spine. If so, stick to the non-sport, it's still verry sporty.
As for the exhaust tone, I may b biased, but I think it's the nicest, non-exotic, stock exhaust tone.
Imo, the rdx is "girly" lookin and might as well get a fully loaded rav4, they're Bout the same size too.
My buddy has a 07 mdx, fully loaded sport, and well it does have every feature u could want, including push button rear hatch closure. But even he regrets getting it everytime he sits in my car and feels/hears it....
Also, I think lexus was too concerned with improving safety/tech on the thing. As a result, it's gotten friggin uglier and uglier with each gen. Seriously butt ugly, imo of course.
Don't get a murano, drives like a minivan, unless of course, that's what u want.

Cheers,
J
Ps. Did I mention the fx rocks?