How much do you have to spend?

In my experience the sound quality of each component overwrites the next item, so it is best to spend a large amount on the Power amp first and then speakers. The pre-amp and source according to taste.

With me cables and power distribution are important so a good 20% has to be spent there. Along with supporting furniture, I build my own.

With all these things you have to audition up and down scale as price is not a precursor to success. I owned a Peachtree iDac this had a galvanic isolator and so I used an AC PSU. This gave me one of the best reports I have heard. So just go listen and learn.

The Power Amp and Speakers are most Important .. approx 25% on the amp and 15% on the speakers would be good, the amp will open up these and provide a good conclusion

IMHO, diminishing returns applies more to electronics (assuming those electronics are not flawed) than to speakers and phono cartridges. Speakers affect the sound  more than any other single component.
I own Ref 3’s, upgraded from R11’s. While a similar overall sound, significantly cleaner & clearer & well worth the investment. Speakers should IMHO be your largest investment by far, with substantially less diminishing returns. 

I don't know much about NAD, or never heard anything exciting about them that would make me try them. KLH speakers, yes, but I agree with the comments above, it's a too many tricks pony, it would be first to replace on my list.

Naim Uniti Atom all in one everything,$3500 do $3500 for speakers you are done if you stream only..

Very happy that I paired a HIROSE RS-520 with the Cornwall IV's. The capability of the RS-520 will meet audio needs for years possibly decades to come. 250W with Klipsch speakers is a bit of an overkill but the HIROSE is extremely clean. Highly recommend it. The combo is a simple one and done setup.