yeah, over time the standard V8 grew from 5.7 - 6.0 - 6.2. We had a semi factory tuner called HSV and Holden started putting LS2 then LS3s into the cars going via HSV. I’m pretty sure the GXP was a GT but with HSV touches like the engine and brakes.
The Holden that Chevrolet belatedly took was basically the VF (the one after your VE based G8) and was just called a “SS” with no Impala or other name attached.
It would have been nice if the Commodore range went as Malibu, Nomad, Chevelle for sedan, sport wagon & Ute.
(Or if Pontiac lived G8 GT, ST & SW. They got as far as running a competition on guessing a name for the Pontiac Ute (with 50 Cent?) (even though I’m sure they had decided on ST).)
But I believe they were trying to avoid criticism from the public about them not being a “real whatever” like what happened with the GTO (from Monaro).