Well assuming money is not the issue and we're not talking about planes for the masses, just for fun.
Personally I think the Gitso is a fine engine as long as you know how to operate it correctly, and lets be honest there's a lot of low time pilots around who have been trained by instructors I wouldn't trust with a Honda Z.
Also was struck this afternoon by the thought of an Aero Commander 500S with a pair of Allisons. Big exhausts out the top of the cowling.
Couple of Nomad engines upside down would do it. That's probably about the size of airframe that SHOULD have had those Nomad engines in the first place.