hi im thinking of upgrading to either a v4,v5 or v6 jdm sti wagon,what are the differences between them? which is the best for safe power gains to 400bhp?what sort of prices would i be looking to pay for one with around 50,000 miles etc?where would i find one? etc etc etc,any advice on this would be a great help,thanks, oh and also what are the advantages over the current uk spec 99 which i already have running 300/300. thanks.