In general, I don’t allocate but work towards an optimal system through testing. Then when I am done, I figure out how much I spent. I have done this more than once on systems upgrades... and in general, it turns out to be about 10 - 12 %. I think it’s at 12% right now.
I have done the same with components and in general have ended up with them at around the same value category each.... streamer, DAC, preamp, phono stage and amp. So all my components in my main system are about $18 - $22K. Generally my speakers are a bit more expensive.