Best sounding amp/preamp for Snell Type E/ll model speakers?

What is the best sounding amplifier/preamp or integrated choice to use with Snell type E floor standing speakers? They are efficient. Specs: 91db Sensitivity, 4-6 ohm Impedance. I hooked them up to a Cambridge Audio Azure integrated (65-70 watts per channel). They sing and sound lovely, that wonderful bass and sound the company was famous for but I  and wonder if they could sound better with a different amp? Are they best with tubes? At some point I am going to pull the trigger on a Freya Plus or Quicksilver preamp but not anytime soon. Other associated equipment I can use now: Adcom 5400 amp, B&K Ref 200 amp, B&K Sonata Pro preamp, Apt Holman Preamp. Any suggestions would be appreciated.