i want to say 9s since 10s on stock are getting common but it really depends on how much you really want to be able to extract from your combo , aftermarket will allow you to get the most but it will take time and knowledge to get there
the only issue with stock and 9's is you need to have the fueling analy correct at that level since most parts are getting pushed to the edge so less room for error and that means individual corrections to each cylinder which as of yet is only acheivable with aftermarket sequential ECUs
stock or aftermarket to get there you need to be able to tune which normally is make small changes see what occured and correct in that direction and continue untill peak performance is acheived , this takes time and on stock ecm with a chip just a few years ago it meant a reburn each step of the way but with current adjustable chips like turbo tweak , me-r and MAf pros and cheap wideband units now giving the stock ecm the ability to correct real time with wideband it makes getting the car that much closer so much easier