I'd always recommend either big push-pull valve amps or Class A solid-state for the modern Tannoy dual-concentrics.
Although the speakers are sensitive, they really come alive with amplifiers that have a decent wodge of current-driving capability, which is not the forte of SETs usually.
Your Sugdens are probably a decent match already, but if you fancy something a little 'warmer', but still detailed, then have a listen to the Accuphase integrated amps, which are a class above the Sugdens ime.