Have I Hit The Point Of Diminishing Returns?

No, you have not hit he point of diminishing returns, not even close! There are many, many levels/steps of quality and dozens remain above where you are now.

I am not saying this to belittle your system; you have great gear and I'm sure it is great sounding. However, the steps of improvement are literally endless. In my system also I do not see the finish line, that is, at a level which cannot be improved. Regularly I have dramatic improvements and have for years.

I strongly disagree with the perspective that you must spend multiples more to achieve a 20% change in sound quality. I would nearly reverse it, and suggest that in trying many different components you can achieve a seeming "100% improvement" in not all that much increase in cost, perhaps twice what you would get for the sale of any given component. i.e. sell for $1K, add $2K = $3K new component. And that is potentially at the upside of what you might have to spend. This is because there is a HUGE variance in component quality from manufacturer to manufacturer.

Example: Some of the new DACs are mind-blowing in terms of improvement of digital quality sound, and you can have these for nowhere near nosebleed prices. The new DSD capable DACs are "affordable" as considered to be truly High End, where some components are priced by the multiple thousands.

I encourage you to do some shopping/listening and experiment with your rig. My experience is that the "point of diminishing returns" is perceptual, not actual. And, yes, changing cables, for instance, will alter the rigs sound most likely in a profound way.

I drive a Toyota Camry, and I'm happy with it. Thus, there is nothing more to gain by buying a fancier, more sporty car.

This is infallible logic, as applied in this thread to audio systems.

Of course, this vehicular and audiophilic logic is driven (pun!) by one thing, a desire to save money. When the OP's question is viewed in this fashion it becomes immediately obvious that one's current satisfaction with the sound has no relation to potential for improvement of a rig, nor to the cost of the system as an absolute predictor of sound quality.

Yet, we have mass delusion in this hobby in that everyone thinks their rig is right at SOTA sound. No one wants to admit they are a long way from the upper echelon.

I'll go on record with this one, given how many CD Players and DACs I've used, old and new; the OP was told in a nutshell that what he's got is good enough. Ok, that's a 2001 era 108kHz 24 bit player - not bad! However, If he takes that advice, he'll neglect the fact that he could go out now, and for about $1-2K, and some at $300-$500, get a 32 bit/384kHz or better DAC that would blow the doors off of the MF player. Have heard it? No, and I don't need to, as my opinion is that having heard it against several 24/192 players/DACs holistically the technology is so far superior to the old that one can nearly universally be assured that the new DAC will vastly outperform, with of course consideration needing to be given to the tonality of the particular DAC as it's integrated into the rig.

Oh, my, that's a real budget buster, an example of what would likely be less than what he spent on the MF player, and a boatload of improvement!

And that is but one example of the types of improvements - enormous improvements - he could have had. :(

Now, if the OP's left the building, taking along the smug assurance that he needs never look again for something better, he'll miss out on it all. Ignorance is bliss, right?

Yeah, he's got his "Camry" and there's really nothing better in terms of performance out there. :(

Macrojack, from my perspective you are the one who seems not to be able to get it. The law of diminishing returns is simple; we get it.

What you don't seem to see is that you have set the point of diminishing returns painfully low, and others disagree, and you have no way to demonstrate that we are wrong. Your opinion on where the law of diminishing returns kicks in is not absolute; somehow you seem to think it is. It is nothing other than your opinion, "...beyond a given point in your refinement trajectory you will pass a point beyond which further improvements come at an ever increasing cost ... that the reward will not be commensurate with the outlay." I have been trying to tell you that you are declaring what cannot be proven.

Jmcgrogan2 gets it, as he points out the same thing, that you are appealing to an absolute which does not exist.

Jmcgrogan2, I find your logic strained. Now that you left the $125K rig you state that the incremental gains didn't exist because you built a rig that's 90% as good? I would suggest you were doing things wrong then, when it came to your high priced rig, because at that point - at any point - one should not settle for a 2%, 5% or even 10% gain/improvement, but more like a perceptual 25% or 50% improvement. It is not worth a lot of money, if I were to state what I consider diminishing returns from a perspective of performance, to gain only a perceived 2% or 5% improvement, so if you were spending big dollars and content with that, I suggest you were vastly overspending to improve your rig. As a consequence, I can see why you think diminishing returns sets in quickly. However, I think it had more to do with your methodology of system building than anything else.

Simply building a lower cost rig that beat the prior higher priced one assembled does not demonstrate that generally lower cost rigs come oh, so close to higher priced ones. If you now nullify your previous impressions/conclusions about the $125K rig you had, distrusting them, how are we supposed to put confidence in your declaration that the lower end rig is so much better? Maybe if you went back to a $125K rig you would change your mind again!

But, you are correct in concluding, "since the return (musical satisfaction) cannot be quantified, whether it is diminishing or not cannot be measured."