I have not heard the La Figaro 339, but did own a DarkVoice 337SE for several years. Not exactly the same thing, I know. I think the A18 is a better amp than the 337SE overall.
I have noticed one thing that maybe some of you other folks can try for yourselves - when running a balanced headphone out with single ended inputs, the top end seems veiled. I currently have my D100 MKII feeding both XLR and RCA into the A18. Using the rear panel switch to go back and forth between balanced and single ended input, there is a large difference in favor of the balanced input. I confirmed by swapping the MKII for the D18 DAC and the Violectric V800 since they all have XLR and RCA outs. Similar results all around. So just because you CAN use balanced headphone out with a non-balanced system, it seems like maybe you shouldn't.... until you get a balanced source as well.
I need to test more with single ended headphone output to see how that is affected by balanced or single ended inputs. I did some listening when I first got it, through single ended inputs, and it didn't strike me as recessed. I've experienced amps that do their best by sticking with the same input and output types, thus avoiding any phase splitter conversions. Perhaps this is one of those amps.