In my humble opinion, the 172 Hawk XP or Reims Rocket is the ultimate in this class. 210hp, constant speed prop, 5.5hrs fuel and can lift 4 adults out of less than 300m. Most parts are standard Cessna and they can be fully IFR.
I have every gadget known to man in mine, Stormscope, TCAD, GNX30, air data computer, fuel computers, engine computers, S Tec AP with GNSS, HSI etc etc and use it extensively for IFR touring.