The classic match would be a LEAK TLA12, QUADII or Radford STA15. The bigger LEAK & Radford valves are also good but the speaker has very high sensitivity so not really needed.
A good DIY solid state match would be JLH's little Class A amplifier. Use HIS improvements. There are a lot of other people's version which 'improve' THD etc but lose the unique features that give it good sound.