UPDATE:
I purchased a used Benchmark LA4 and a pair of PS Audio M700 mono blocks from a seller listing both. Got a great deal on the LA4 by also buying the M700 pair. I honestly expected to flip the M700 pair.
The LA4 was an amazing upgrade over the NAD C165BEE. It should be at double the MSRP. The improvement was more than I expected with wider soundstage, a bit more depth, and improved separation. After a couple of days I then inserted the M700s in place of the Nakamichi PA7Aii. I was not expecting any improvement and was hoping to sell them and look for something else in the future. There was a definite improvement in clarity and instrument separation (essentially what I was initially hoping for with the LA4). The end result was more than I had possibly hoped for. The confirmation came from wife when she said, "the stereo seems so much clearer. I like it."
I listed the NAD and Nak for sale and the Nak sold almost immediately. I expect the NAD to sell soon.
This got me thinking what else should I upgrade. It didn’t take long. I just purchased a PS Audio DirectStream Mk1 DAC from TMR. They are having a great sale on refurbished PSA DS Mk1 units. Should have it in a few days to replace my Bifrost 2/64 (may sell, or move to my 2nd system).
Hopefully I am done with my case of upgraditis.