Are you able to get good bass when you crank the volume? I have the HS paired with a Willsenton R8 tube integrated and the bass is tremendous when you let it rip, lets say 5-10% before clipping or between 9 and 11 o’clock on the dial depending upon the song. What can be really confounding about the HS is that at lower volumes the bass becomes much less noticeable due to the prominance of the highs and mids which stay full sounding regardless of volume. You really have to push the tubes to get the bass. It’s a great low volume speaker due to all that detail, but it won’t shake the room. I imagine you’d need a really muscular Class A or AB design to get the low end at lower volumes.
It seems like your bass problems have continued despite moving to the QLNs, which makes sense since its still the same amp. I have a new preamp coming, I’ll be able to test the HS with my SimAudio W3 later this week and see if that gets better low volume bass results. The Sim isnt a Wattage monster, 240 watts into 4ohms, but its a high current design with a massive 1.1 kVA toroidal transformer.