Assume you can afford the next step-up only.
I would go for a Jetprop. It offers a real increase in capability – 260kt TAS at FL260 – and not just an incremental one which say an SR22 would offer.
If you mostly fly alone or à deux, it’s fine, but it soon goes overweight if you push it.
Phenom 300 is my current wet dream.
Sadly it doesn’t exist but if it did it would be a
PA38 with a Rotax engine in it and a convential tail to lift the nose wheel out of the mud on the 550 meter grass strips in mid winter
If we talk about the next step up from a C172, I’d want a six seater SEP, either a PA-32 or a A36 Bonanza. What I need is a roomy cabin, payload and speed, while range is mostly irrelevant as I’d not want to fly legs longer than 2 hrs.
PA38 with a Rotax engine in it and a convential tail
I think that‘s called the Sonaca 200, no?
I would buy a 4-place (4 useable seats!) retractable with short field/grass capability. C182 and C210 come to mind. Auto gas STC would be nice.
Any TBM or JetProp as the second best choice. Going for any jet would be overkill even in the case that finances are ok because that would mean no local one-hour flights at (kind of) low level. I guess that in SET you still don’t pay a lot of penalty in fuel for flying at FL180 or so.
I sometimes have envies of a faster climbing, more capacious plane than my current ride (PA46 piston). The M600 would be very nice for example. But then I go for a low and slow flight around the Isle of Wight, and I can’t really see myself doing that with a turbine (I may be wrong). I also remember than in 5 years, when the kids are grown up and gone, I won’t need so much weight carrying capacity… I’m very happy with my current plane, actually! My wife dreams of a PC21 though.