if you want the best, it is not enough to buy costlier gear pieces, you must understand for example what this % of improvement is about, acoustically speaking, what may be the trade-off cost, etc...
Timbre naturalness is not immersiveness, which are not sound source width etc ...
if you dont understand how to work with acoustics conceptual parameters, paying for more costlier gear is throwing off money in a blind obsession..
The diminishing returns principle is not merely about the gear investment but also about your lack of acoustical understanding investment...
The gear design engineering may improve but your own understanding must improve also because you must learn how to use the gear if you want a positive return from investment ...
The principle of "diminishing returns" from gear design limitations and potentials is the reciprocal of your "increasing acoustical return" learning abilities...
If you want the best you have to tackle that last .000001% of performance. Plus it has to look the part.