at the top of the food chain %’s don’t mean much. chasing ultimate sound breaks all the rules. i don’t hold my system up as any sort of example on what to do.
but if asked what’s a good approach starting out or at modest levels, i would say that (1) getting the right speakers for your room and (2) stretching on the budget for speakers likely will result in the best sound. whether that is 50%, 75% or 90% of the budget for speakers......is ok.
these days perfectly competent amps and sources (even skip a preamp at the modest price points as they typically limit performance) can be found on the cheap. and entry level sources and amps with good speakers scaled to the room with bring the best bang for the buck.
the speaker<->room interface trumps all.
even more essential is having a sonic reference you are aiming for, otherwise it's a game of chance. if you don't have a good idea of the sound you want then find someone you trust and allow them to assist you. or don't buy until you hear something that satisfies.