After listening for a couple months, and swapping back and forth, I consider the tube change quite significant. The Reflektor tubes, along with the Synergistic Research Black Quantum fuse are the most significant upgrades I've made, even more so than the power cord. The mids are smoother, and the highs are cleaner. More crystalline. Quite an improvement on piano realism. I'd say, for about $650, the change was well worth the expense.
