I owned avanti's for a few years. In general, they do not need much power & they favor high quality components and revealing cabling.
Off the top of my head, the best combination I can think of would be:
Audio Aero 24/192 cd player direct driving an ARC v100m2 tube amplifier with svetlana kt88 tubes. Use a nordost quattro-fil ic to connect them & use nordost spm speaker cables.
I think the best solid state for them is pass labs. I used mine with the aleph 2 100w monblocks & aleph P preamp. I later moved up to an X1 preamp. I haven't heard the x series amplifiers yet.
For tube electronics, I had two favorites:
(1) The BAT vk-5i (or vk50se), and an arc vt100
(2) A 15 watt Cary 300 SEI with Western electrics.
For cabling, I found Nordost quattro-fil was my favorite for ic's with SPM speaker cables. I also had good sound using the acoustic zen satori speaker cable. It's a little slow and syrupy compared to spm, but has more harmonics and can tame a bright top end.