Interesting question. I have been lucky in that I had a business for about 15 years so got to have a bunch of gear in and out without personal expense.
Of course much will depend on your musical tastes. Don't have strong disagreement but depends a bit on your room. If your room is good already, you need to spend less, if its not, you might do well to spend more.
Regarding speakers and subs, the numbers very reasonable but its not always simple to integrate subs and there are some pretty good speakers with decent bass to avoid this. Just my opinion of course.
In my experience I noticed more from having a good preamp than better amps, but again just my experience.
Above all, enjoy the journey.