All things considered, it's a bit much to call any Amp a knock-off or rip-off of another. All valve amps are essentially variations on three or four old RCA circuits for audio amplifiers. They might have more tubes in one bit, or varied values of resistors or whatever, but they all come from the same source, ultimately. Even Marshalls started out as a jerry-built "knock off"/homage to the Bassman using the components available, the Bassman itself being a small variation of a design for Audio amplification that had been knocking about since god was a boy.
Circuit wise, there's not that huge a variety of things going on in valve amps. The differences come about through quality of components and selection of Resistors, caps, valves and Transformers to suit a tone. If the Brugera amps have decent components, they'll sound good (or at least, like what they're meant to sound like), if they don't, they won't.
