I brought a 2004 Jaguar Xj8 3.6 Sport as a foil to the MX5. I’m really liking it as a drive. It has a split personality; you can waft around town like Lord Snooty, then on the back roads, the active suspension makes the big car surprisingly nimble on the twists. I like details like the suspension dropping it self by 20-30mm on the motorways for better efficiency. Or the whole start up sequance; when you pipe the keye in, the seats, wheel and pedal box all automatically adjust. Averages 26mpg, I can average 38mpg on a motorway run, so about the same as my Mk1. Its not the full fat XJR, with the supercharged V8, but it has the same interior, and suspension set up. Cost me £4500.
The drawback, which will also affect the BMW 600s and possibly that SLK, are that repair costs are high. Parts prices are outrageous, but then, in 2004, my Jag invoiced for nearly £50k. Mercedes use a lot of the same parts across their range, so some parts are ok on price (same bits as a Bonn taxi). They are all heavy cars so will eat through bushes. All of these cars have terrifically complicated electrics, that will be problematic on a 10-15 year old car. I read that BMWs, once they hit 100k, the chassis loosens up, and they feel terrible. I had a E46 before, but wasn’t impressed by that; I think the 3 series is little more than a disposable car. My sister had a 330 coupe, later shape. It needed a new engine at 100k, and she ditched it for a Mini. Borrowed a WRX once (bug eye version); the interior was horrendous, and not a nice place to be. You have these grippy rally seats, which are not comfortable, and then just acres of grey plastic, I think the one I had even had fake stitching. Its just a jumped up economy car with a 4WD gimmick.
My Jag is about 260hp, the 4.2 NA is 300hp, and the 4.2 SC is 400hp. They all cost about the same; £4-6k will get a decent one with history. I was put off a XJR (did look at a 1 owner example) by the valley hose; a £20 hose hidden under the charger. Takes a day to extricate it.



I like it enough that I fancy a XK8 next (its just me that drives it, back seats never get used).
350z passed me by; its a car that never really left a lasting impression.
Miataforum gives fairer feedback on different cars than Pistonheads, which can get a bit tribal. Obviously, Miataforum can only really reflect cars sold in the US, but the ones you are contemplating are all sold there.