Funny. When I had Normans RK 300b to test I first listened only to the RK 300b and I really liked them. In fact, they reminded me very much of 242
But when I finally i serted my 242 again, it became obvious, that they are really very similar but that the 242 just do everthing a bit better.
Without direct comparison, I would have been happy (enough) with the RK 300b, but as it is, the 242 remains the Queen in my castle
When you factor in price (632 Euros (versus 999 Euros for the RK) or 781 Euros inc 19% VAT, Paypal charges and shipping) I'd say the AD1 looks great for anyone wanting to take a punt. And the RK looks really quite overpriced.
I wish I could use AD1 with the original socket type. Fitting the Lampi with Yamamoto AD1 sockets was a step to far... Though the valve with UX4 sockets is 50 Euro cheaper.