Finally.......Pleasant sounding strings on a modest system

Hi, I'm new to posting here, I guess there's more free time these days. My ultimate test for a stereo system is how well solo piano and symphonic strings are reproduced. I figure if a system gets these right, everything else will sound good too. (to test bass, I throw on some Marcus Miller) For years, and with many different speakers/amps, I've been frustrated with the sound of the violin section of symphonic recordings, even when it seemed to be a good recording. I made some changes to my system in the last few months and I finally have enjoyable sounding symphonic strings and solo piano from my CD's. My only source these days is CD's, having sold off all my LP's in the 1990's and not up to speed yet on streaming. The first change I made was switching the power tubes in my Prima Luna Prologue from Gold Lion kt 88 to Tung-Sol 7581A . I always heard a hard, glassy edge in the treble with kt 88's even though I liked the muscular bass. This new tube reproduces the treble more smoothly, with good clarity and articulation and also has strong bass. The next change was lining a portion of my speaker cabinets with sonic barrier, the one with the copolymer layer, which tamed an annoying hot spot in the midrange. Then the final change was the addition of an R2R DAC which created a more smooth, organic sound to my ears. Now considering a dedicated cd transport. But so far, these 3 changes have made me a much happier listener.

My system:
Prima luna Prologue
Tannoy Revolution xt 8f
Denefrips Ares II DAC
Marantz CD 6006 as transport
non-exotic cables (Blue-Jeans)