Just to share some experience with the 300B. I have the original Willsenton R-300B model from a couple years ago. That one has a balanced set of inputs. Very nice amp. From rumors online I believe Willsenton are made by the same factory as Cayin and Prima Luna. You can see the resemblance to Cayin in build with the newer version Willsenton R300 model.
I also have the Muzishare X9 (made in Line Magnetic factory) which in addition to 300B tubes sports Nichicon filter caps and Mundorf coupling caps although at a higher $1700 price point. The sound from that amp with Klipsch Heritage line of speakers is magical.
Looking to find a little more thump for my Forte IV I did decide to also give the Muzishare X10 a try (SET KT-150) at 25W per channel. Just received it today. Bass thump is there at the slight expense of the organic magic of the 300B tube (which lacks a bit on bass control). The X10 is more resolving and in control of the music while the X9 flows with the music.
So a trade off between the two but both excellent depending on your particular music tastes - Jazz versus rock etc. Although both amps have not been in my collection long enough to truly break in yet so I expect a decent amount of improvement in tone over time.
Looking forward to more reports on the Willsenton R300. Does the remote do finer increments on the volume pot now that prior models? That was my only real complaint from past Willsenton amp models. Otherwise they are fantastic sounding and a great value.