I think a Lunatec V3 (or V2) sounds fantastic behind a pair of Gefells. I know a lot of people also like a pre-amp with transformers behind gefells. something like an Aerco MP2, Oade m148, PSP-2, or Neve Portico 5012. All of the pre-amps I've mentioned would sound great with the gefells. Ultimately, it will come down to what you prefer.