I keep looking as do others for the tranny you are wanting. there are a couple of choices, the Quaife being one of them as the link to that thread indicates. all are about the same $. if you really want it, you are going to have to pony up.
500 hp is achievable with different engines that wouldn't compromise the handling, but if applying it any direction but straight line, the Esprit chassis is more likely to generate drama than a smile; it hasn't changed significantly since 1977! IMO the car is too light that anything above that number wont get to the ground.
I'm with you on more power in a great looking car though: after driving 500mi I was nearing home when I encountered a 997 on the interstate, I fared very badly and decided a rebuild and upgrade was in order. now I believe I will lose more gracefully and at least raise an eyebrow or two for a classic car.
I dream of ridding my Esprit of all its inherent flaws either in design or age of technology, but have limited monetary commitment as do most of us
im still chasing that dragon. have you seen CHANGES car? 424 hp, so much $$, almost no trunk space left and still mod'ing to accommodate previous mods
did you read MT Z28 vs Hellcat? the Hellcat is certainly a throwback to the American musclecar philosophy of the period! its a tire spinner for sure! big grins that will wear thin after a while if it was in my stable
the guy who owns Artie's Esprit has a C7 with magnetic shocks and has good things to say about it...