Yeah, the low end is one of the big things I love about the BDA-2. Great sub-bass performance and so much better than the W4S DAC-2 (actually not even close here; as far as DACs go that is) and
on par with the PWD2 in that regard with direct A-Bing. Any more bass would be more than what I consider as "neutral".
I guess another preconceived notion (or prejudice) I've had with NAD that held me back is that my experience with them in the past 20 years (now I really feel old as I see you're about that age
) is that they are a great entry level (many of their older CD players) to mid-fi audiophile company. Could be that the M51 is a great DAC and I hope to hear it soon, but if it has more bass than the BDA-2 or PWD2 (which I consider about equal in terms of bass impact), then I'm glad I went with the Bryston.