just curious why you would rule out the 556hp 551 lbft CTS-V on account of it not being turbo, but let a less than 350hp mazda speed 6 stay on the list?? Your talking about a car that was intended to do the same thing as the LS. It took longer for the Catera to evolve, but that CTS-V will spank Z06's, M5's etc etc etc!
AWD.... CTS4, still has PLENTY of power and runs on regular unleaded.
G8.... wait till spring, GTP is coming out with 400+hp.
non american.... Acura TL type S (back to premium fuel though)
other ideas.... used 5series xi (or new, but I dont have that kind of money), i dont like audis, but they have a massive following and there has to some reason for it, infinity g37x, nissan maxima (not sur eif they have an AWD option)
of the three you listed I'd go Volvo. I personally dont like that blue, but the red and black ones look good. You can see the LS like design in the pics of the two next to each other.