I don't have a formula but I have a few rules that I try to follow.
Analogue front end should be very strong or all will be for nothing. I believe that the table itself is the most important part of it, then the arm, then the phono and then the cartridge. Good $350 MM cartridge sounds excellent in $1500 arm and $4000 table through $1500 phono. That's what I have. One day I will upgrade the catridge and the phono, preferably at the same time and preferable to something about three times more expensive.
The speakers. I keep them for a very long time, 15-20 years, so they must be good. I don't think that there is anything under $10k that I would really like to upgrade to, so for now I keep my 17 year old speakers that used to cost $1500 new.
I buy everything used except cartridges.
So yes, as you said, whatever sounds great, taking the cost into consideration.
Analogue front end should be very strong or all will be for nothing. I believe that the table itself is the most important part of it, then the arm, then the phono and then the cartridge. Good $350 MM cartridge sounds excellent in $1500 arm and $4000 table through $1500 phono. That's what I have. One day I will upgrade the catridge and the phono, preferably at the same time and preferable to something about three times more expensive.
The speakers. I keep them for a very long time, 15-20 years, so they must be good. I don't think that there is anything under $10k that I would really like to upgrade to, so for now I keep my 17 year old speakers that used to cost $1500 new.
I buy everything used except cartridges.
So yes, as you said, whatever sounds great, taking the cost into consideration.