2006 Jaguar XJ-Series XJ8 4dr Sedan (4.2L 8cyl 6A)
One of the quietest, smoothest rides you can find. And, if you do your research, you can find genuine bargains. I paid $33k for a 2006 with 18k miles, with an 84 month/75k mile warranty. Seats are comfortable - this is one of the best cars you could ever have for a long trip. Stereo is fantastic, nav is easy to operate, and bluetooth syncs easily with most phones. Surprisingly, gas mileage is very good. I average 18-20 in the city, and 27-29 on the highway. Handling, although far from sports-car like, is quite good. Overall, this is a fine car, much better than other cars in the same price range.
Air suspension gives an amazingly smooth ride. Stereo is top-notch. Interior design, although staid, exudes luxury.
Seats, although comfy, could be better - 4-way adjustable lumbar would be a big improvement (2007 and newer have this). Also, I am not a fan of having to use the nav touch-screen for climate control - too many screen changes required to simply turn A/C on or off.