Of the above 4, I only considered the Jag and the Porsche. The Jag is much more of a GT than a sports car -- and is quite a bit more comfortable for driving around in. It's easier to get in and out of, and certainly is a lot more powerful than most of the 911s until you get into the upper range of them.

The cars I considered (as I was after a convertible) were the 911, MB SL, BMW 6, and Corvette. The MB and BMW were just... soulless. Competent and well put together, but... boring. The 911 is always a great choice, but you also see a ton of them on the road. And parts for them (at lease here in North America) were considerably more expensive than either the Chevy or the Jag.

There are lots of opinions on the sound system. Personally, it's a fairly accurate system in terms of Sound Quality -- especially if you have a good source. But it's not particularly loud in terms of Sound Pressure. So if you're using MP3s or Satellite Radio, just be aware that often times it's not a particularly good full range source.

I went through all this only a couple of months ago, so it's still fairly fresh in my mind.

Good luck! Sounds like a 'fun problem' to have.

 

Not considered a Range Rover Sport? more practical where you are. I personally wouldn't use a sports car unless you know the roads you can enjoy?
As for the stereo, it's best in class, B+W actually worked with the JLR group to integrate the sound systems tailored to each vehicle.
See if you can test the car before you pull the trigger.

 

I agree with Rahtok's comments. What's not clear to me is whether the XKR will replace your XF-S or be an addition. If a replacement, there's no question you should go with the XKR, especially given your road conditions. The other cars sit lower and ride harder. If you plan to drive the car every day, I think you could get tired of the other cars you mention for the reasons Rahtok states.

If an addition, you have a bit more flexibility. Then it's more a question of which car offers the character you desire. You can afford more compromises in ride quality, and ease of getting in/out because you won't be driving it every day. You might then like the handling of the R8 as a nice change. It's closer to an exotic than the other cars, and yet fairly practical.

The Porsche is quite simply very competent, though I find them rather uninteresting to drive.

The RS5 is closest to the XKR, but I'd easily take the XKR over it. The XKR rides better without any real handling compromises, and is at least as fast if not faster. Both are beautiful cars but I like the Jag's lines better.

So if a replacement, the choice is easy: get the XKR. If an addition, for me it's a tossup between the R8 and the XKR.

Finally, congratulations on your business success allowing you to reward yourself in the first place!