HARBETH: Amp for Harbeth P3 ESR Croft, Brio R… ?

Having down scaled slightly and dropping on these little gems, I'm looking for suggestions for an amp to get the best out of them. So far I've tried my EAR 859 - beautiful but not quite capable of driving the bass solidly, a sugden a21A kindly lent to me, again beautiful if slightly restrained and still not giving the bass enough definition and drive. A rega Brio R probably the best compromise in terms of overall presentation and beefs the bass up superbly.

I'm considering more powerful valve amps such as a unisis which I've owned before and loved primaluna and also the likes of the newer Croft stuff so would value any opinions on this and the Brio R as a comparison before I just buy the Brio. Thanks.

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