I'm really doubting some of the facts you've mentioned.
Buying a brand new car is stupid, costs 3 times more, go for used one, in great condition.
3 times more? Not even close. I'd say if you compared a used 2012 with 10k on it, to a new 2013 or 2014, you'd be looking at a 15-20% drop, not even close to the 66% you are talking about.
If I wanted a sport car I would go for Skyline R34 with GTR engine 2.6 twin turbo.
As Leith mentioned, it's his first car, and what you've mentioned is far from a daily driver. Between the twin turbos and the fact that they were last made in 2002, I don't think Leith wants a heavy maintenance car like that.
If you need just a beautiful, quick sedan, buy M6, I've had a chance to sit in M6, it's awesome.
I don't think sitting in a car gives you much of a feel for it. I drove the M6 for several months, but I didn't like it that much. If you're buying one, the 2012+ M6 is much nicer than the ones made in 2010 and prior. Entirely new features and style. Anyways, his budget is like $13,000, not $70,000, so I don't have the slightest clue why we are talking about an M6. On another note, I don't think the car was ever made as a sedan, it was always a coupe or convertible, so that just tells you how much knowledge 'sitting' in the car gives you. You don't even know how many doors it has.
As for Jeeps, Range Rover sport is my favorite, so you've got a huge choice.
I believe Leith is from England, and I don't believe a Jeep would be a cheap option over there as I know when we bought the Range Rover, we had to pay 5 figures just to import it (English car), and I think it would cost Leith the same to do vice versa, import a Jeep. If you do decide to go with a Jeep, you should go with the SRT8 engine. Either way, I don't recommend the Jeep or Range Rover for the purposes you explained.
Leith, I don't know the prices over there, so it's difficult for me to recommend something. If you had $20,000 and were in the USA, I'd recommend a 2008 BMW 3 series. I believe they are around that price tag.