oh boy, can't believe it? so every body says Caffein is better than Royal one? can please be detail in which aspect regardless cheaper price?
I think they are very good amps for the price, and the Caffeine Pro/Ultra gives more bang for the buck. The ultra uses an LM6172 like the Lyrix in the ground channel instead of a TI rail-splitter, for more current delivery. It performs on about the level of a Meier Headsix or RSA Tomahawk and it sounds a little better than the iBasso D2 Boa (but maybe on the level of the D3).
I would not hesitate to recommend a B-stock for $49 as you would have to spend 3-4x that much to match or beat the performance.