I was in a similar dilemma as you when I had the NAD M50.2 hooked up to a PS Audio DirectStream DAC. Both were good components, but I was missing something, so I went on a DAC hunt. I moved through a number of DACs, including a Lampizator Baltic 3 with over $1K of tubes, but ended up returning it. When I decided down the other path and added an Aurender to the chain, it made a much bigger difference than continuing to upgrade
A clear example of a lower quality streamer mitigating the performance of a good quality DAC. This is why placing over emphasis on the DAC and relegating the streamer/source component to 2nd class status is a bad idea. A compelling case could be presented that in a good/high resolving audio system the source and DAC have equal sonic influence. Lower resolution systems will very likely obscure the impact.
Charles