I have had a similar experience to you and can make an informed recommendation for a potentially good DAC to try. I have a Luxman L-550axii amplifier which is quite warm, smooth and refined like your Accuphase. I also use a Bluesound NODE as source, just like you are planning. I found a good DAC with synergy to be the Chord Qutest which cost me about £800 in the UK. It is very good at excavating detail which balances out the smoothness of the amp. I find USB to be to clinical for my taste and prefer to feed it with an optical cable because that sounds more organic to my ears and has the benefit of preventing any electrical noise from entering the DAC. It doesn't have balanced connectors though, only single ended. The Qutest has three gain settings to choose from; 1v, 2v and 3v, the higher the voltage the fuller and more impactful it sounds, I use it on 3v. It's a bit quirky to use but full of character and they seem to hold their value.
PS - I found this website because I'm thinking about the E-380 as a potential upgrade so I have a bit of an ulterior motive in recommending the DAC I use. But I think it would be an option worth considering alongside the R2R DACs others are suggesting because I think those might be too smooth with that amp, too much of a good thing.
