A good DAC in the 1k range will sound great. I think audio-gd does a great job.EF6 isn't endgame but it's easily beaten by integrated speaker amps in it's price range.AVC stands for autoformer volume control. Mine is a custom 4 channel made to my request. I waited about 4 months.
I've listened to the EF-6 a few times and always thought it was a pretty mediocre amp. HE-6 is not susceptible to changes in DACs. I'd say keep upgrading the amp.I heard their reference stack or whatever at CJ. Laughable at best. My rig completely smokes it at half the cost.