You need loads of power to get above about 150kt IAS.
With lots of good aerodynamics, and lots of fuel burn, you can get a piston to go to ~ 180kt IAS.
Certified planes are stuck with a Vs of 60kt, and unless you have flaps the size of [insert as inappropriate] it is very very hard to get an IAS more than 3x Vs. Homebuilt planes can have a higher Vs of course, as can multis.
The way to get speed is to fly high. A Jetprop does 160kt IAS at say FL270 and that is about 260kt TAS. Same story for everything else. Concorde's IAS was only a few hundred kt, IIRC. But the oxygen issue then starts, and if you want total care-free comfort you need pressurisation, which is why all that hardware is so big and pricey.
I'd like a turboprop version of my TB20, and a FL250 ceiling.