Thanks for sharing your review on the Reisong A10. I was also looking into this tube amp and glad to hear you enjoyed it so much. My thoughts are the same on tube amp pairing! Instead of the Reisong, I wanted something more future proof and purchased the Willsenton R8 tube amplifier pairing with the original Sierra 1’s. I was previously using the Cambridge Audio 540a v2 and Harmon Kardon AVR 2600. I had no problem using those with the Sierras but was always curious about tube amplifiers. I first tried the Monoprice hybrid tube amplifier and that did not work out at all. The sound quality was a complete downgrade but I did like the looks a lot. Here I am today, enjoying the Sierra 1’s with the R8 and everything sounds better. Similar to you, overall a fuller sound, more warmth, punchy tight bass and beautiful vocals. Almost like the speaker transformed. I’m just a casual listener and my focus is a minimalist two speaker stereo system. I first started my Ascend journey 15 years ago with the 170’s, to the 340’s, and shortly to the Sierra 1’s with HSU MK2 subwoofer. Although with a budget constraint, now thinking about the Sierra 2EX if I can get it used or bstock to complete the system.