I echo the remarks of Akg-ca. In the past, I owned the 162/272 combo; now I own the 375.
Turn the soft clipping switch to off. Turn the tone controls off. Replace the pre-to-power jumpers with ICs. Replace the stock PC. This will take your 372 to its peak performance.
Two areas I'd encourage you to consider before changing anything with your 372 are: (1) clean power, and (2) room acoustics. I've read countless times on this forum that we listen to the power and the room.
With respect to digital, you might want to insert a DAC between the CD and the 372.
NAD seems to bring out polarizing opinions on these forums; people usually either love 'em or hate 'em. IMO, you need to spend somewhere in the $1500-$2000 (used) range on separates to measurably improve on the 372. If you spend less than $1200, you are just trading one flavor for another. For $1000-$1200, you can make several purchases in cables, power, and room acoustics that will have an improvement on the sound and not just a flavor.