Integrated Amps

I'm debating whether to upgrade my Marantz integrated with a better performing and higher powered integrated or simply add a separate amp and use the Marantz as a pre-amp. I've looked at stepping up to the Marantz model 30 or 40n, PS Audio Stellar Strata, Music Fidelity M5si/M6si. But then the Heaven 11 Billie caught my eye.

Has anyone had any experience with the Heaven 11 Billie integrated amp? It's a hybrid class D amp w/ a tubed pre-amp. The reviews I've watched seem to give the unit high marks for sound quality, presentation, sound stage, and because of the tubed pre-amp, an analog warmth to the otherwise "cold" sound of a class D amp. 

https://heaven11audio.com/billie2-amp-features-specs/?v=7516fd43adaa