K6's. The C7 RADIAL driver in an M30 sized box. Been out of production for a few years, picked up a secondhand pair out of curiosity (three people who have similar tastes to mine kept raving about Harbeths, so I don't deny that gave me the idea to find a pair to try myself), and I found like them enough to keep them.
Naturalnesss is about right, I'd say. The -3dB point is 45Hz, don't know if that's deep enough for me to start boasting about the size of my low-end. Can anybody advise? 
-- Ian