I've bought three pairs of these a few years back; one is performing very well on a trioded el84, second pair on a lesser 6ck4 being rebuilt for 'RH6v6', third pair unused for now. Price/FR extension seems hard to beat (there's a FR graph somewhere on the website); haven't heard any of the high-class SE trafo's. I must add that Jan is a pleasure to do business with.
Simon