The Backert Rhumba Extreme really interests me- unless I can find a used VAC Signature MkII SE
These two have different sonic signatures, so at this point it’d be good to ask what sound characteristics you’re looking for as that will make all the difference. Given what you’ve said about wanting to keep the upper detail of your D3s I’d skew to the Backert and also mention the Linear Tube Audio MicroZOTL or MZ3 preamp (depending on your connection needs). I’ll also reiterate my prior recommendation for checking out the reviews of both the Atma-Sphere and AGD GaN amps that are getting rave reviews as being a wonderful combination of tube goodness with solid state control and are upgradeable. Best of luck.