Pre-Amp for Class D Amp

Yes, tube active, lush even, to round out stark but clear class D and detailed B&W. Maybe Conrad-Johnson. Perhaps a pre which uses 6SN7's. Cary SLP-98. Stay away from passive pre's with D class amps.

I use Audio Research sp16 with my Bel Canto REf 1000m amps and can easily recommend it for top notch sound.

REf1000m amps specifically have high 100kohm unbalanced (higher balanced) input impedance which makes them very compatible with tube pre-amps.

Class D and tube pre-amps in general are a match made in heaven, especially when amp is designed with higher input impedance to optimize the mating.

I agree with a tube preamp suggestion to go along with your Class D type amps. I have a budget system and am finding great synergy between a Xiang Sheng 728A preamp along with Red Dragon Audio M1000 Mk1 monoblocks. I had the 728A modified though to accommodate 6X4 rectifier tubes and the required adapters for them.

I have tried The TRL Dude, Conrad Johnson Premier 16LS, EAR 868, eastern Electric Avant, all tubes, and all sound fantastic with my Bel Canto ref 1000 M amps as well as with Class D audio SDS 470 amps. Tubes, tubes, tubes the key !

Any decent tube preamp or buffer stave would go nicely with Class D amps. As mentioned, tubes are the key to a well balanced system using Class D amplification. We have been designing around Class D for several years.
The Bel Canto's have a high input Impedance, 100K/200K ohms so there are no concerns there. They do have a rather high sensitivity at 3V but again, most preamps will drive them to full power with no problem