In my opinion going from a ve ss to a stagea is a backwards step. It's 10 years back in time, heaps less safety and an engine that's not going to be in as good condition. Your current ls engine will take a beating and keep giving. An Rb26 will spin a bearing, then cost more to fix ( labour etc) massive import tax for insurance and parts.
Stageas seating position is stupid high. I am 6ft 3 and with no sunroof just fit. With a helmet on don't fit. Sunroof would be worse.. Perhaps the rs260 seats are lower, and I would hope so as I had to put gtr seats in mine to make the head room ok.
They are also heaps smaller than a commodore, so rear seat room is basically non existent. Boot is a reasonable size I suppose, only cos it is a cube.