The thing with the MX-5 is that it's got a chassis that just makes you want to thrash the living daylights out of it and at the sort of power levels they have as standard (160 odd BHP from the 2.0 NC we have) you can do that all day long without it ever getting seriously out of shape or losing your licence. There'll always be long straight bits of road where you wish for a bit more grunt, but on the twisty bits where it counts it's more satisfying to have to stir the stick a bit to keep it going rather than have a big V6 where you just leave it in 4th and use the torque.
Adding more lots more power to a chassis that encourages its use is no longer something that appeals to me. I also dislike the size of modern tyres, which removes most of the progressive and predictable nature that older cars had. Now you have lots of grip until suddenly it all disappears and you're going fast enough to need more road than is available just to attempt to gather it back up.
I realised several years ago that I've never found really fast cars fun, it's driving them hard that I enjoy not the speed. My tweaked 2.9 Capri was so effortless that I regularly missed my turning because giving it 2000rpm in all of the gears - really babying it - meant I was doing about 80mph in a 30 limit. A 2.0l will do that, but you have to want to. They're better balanced too, big roundabouts on dual carriageways can be taken without slowing down, but all four tyres just on the limit of losing grip whilst howling musically
I've tried all of the MGFs that various friends have owned, and the best ones are the original 120hp solid cam cars.
Similarly, I'm too much of a wimp for motorbikes and I've seen the results of inattention too many times.
Given a lottery win, I would be ordering a Caterham 170 for the same reasons - it's fast enough without being utterly terrifying or even particularly illegal.