Each one of those cars featured significant and functional performance upgrades, but comparatively speaking, pretty standard stuff.
Standard enough such that E92 M3 or 997 911 S owners could create near performance equivalents with aftermarket components. The M3 GTS in particular has been virtually replicated, and even improved upon many times over (minus the stroked engine) by BMW track junkies.
Good luck creating an AMG GT R equivalent.
More than perhaps any other car of its kind, the flagship Mercedes-AMG AMG GT R utilizes modern technology as the foundation of its prodigious track performance.
The active aerodynamic elements in particular are cutting edge.
Additional aero elements include an adjustable rear wing, (gorgeous) double rear diffuser, and two vertical air curtains that optimize air flow into the wheel wells.
AMG GT R power is derived from a 4.0 liter, 585 horsepower V8 in a "front-mid-engine" layout. The GT R gets the same 7-speed AMG SPEEDSHIFT dual-clutch transmission as the base GT model.
The AMG GT R looks to be the new benchmark for the technological end of the track car spectrum, cars like the BAC Mono the other.
So long as track cars of both distinct varieties continue to be offered we have no complaints.