Hmm, all those multi-valve engines are OK at the top end but they are not very "grunty" (1.8T excepted) and I like "grunty"
I have thought about a G60 or even a VR6 (both available from Corrados) but the latter is perhaps a difficult and thirsty conversion...
I even wondered about grafting the G-lader supercharger onto the existing engine - VW did something like that on the Golf....