AC dealer here. I have written up a direct compare of the Helene vs. other DACs in another thread. This unit is very fairly priced and quite competitive in its price class when you consider its feature set (DAC only, no VC or streamer).
The sound is detailed but remains natural and analog sounding. Tubes do not add warmth but texture and pleasing harmonics. This is not a warm DAC but also not bright. The image is massive with good depth. Sonically, it is wonderful and works well in a LOT of systems.
Few notes, USB is by far the best input and what it is optimized around. It will sound best if you have a source that is optimized around USB. The tubes are uncommon and pricey $300 to $500 each and if you leave it on all the time you will replace them once every 12-18 months. If you turn it off...they will last a long time but then you have to wait for the DAC to warm up which is a solid 20-30 minutes like any tube device.
The unit is wired in reverse phase. This is not a problem for 2 channel speaker listening. If your system lacks a phase switch you can just reverse the speaker cable wiring. It is a big problem in headphone systems as you either need that phase switch or you need to have custom cables made.
The unit is very competitive with Esoteric, Playback Designs, Rockna, Linn which all have offering in this price range or a bit above when you control for feature sets.