The 207 is good value for money and a proven performer, however more capacity and stroke will make you more torque and possibly power .... how long is a piece of string ?, how fast do you want to go and how much money do you have ? How long do you want it to last ?....I could go on..

Power is made from the block upwards anyways(or block outwards in the case of a subi !)

Don`t know what the above stuff about piston-valve clearances is about but all 96/97 on Turbo EJ`s have virtually the same piston deck hieght and head chamber volume, and big cams has never been an issue with 207`s AVCS, non AVCS/whatever, older heads newer heads etc etc ...its not like its a high compression n/a engine, its got a hairdryer for cylinder pressure