Just my 2 cents but $200 for a pair of Chinese 6SN7's seems a bit much even if the Sophia's do sound very good. There's still plenty of NOS available and most for less money.
Life expectancy would also be a concern for me. In addition to owning numerous versions of NOS 6SN7's, I still have several NOS Telefunken E88CC(6922) and ECC83(12AX7) tubes that have been used in five CAT preamps over more than a dozen years. Those tubes still test like new. The Sovtek's and Electro Harmonix that came with my first CAT didn't last 1500 hours. Yah, I know, we're talking 6SN7's but I'm guessing any good NOS will last waaay longer than anything produced today. Some of those old 6SN7's were rated for 10,000 hours!
Life expectancy would also be a concern for me. In addition to owning numerous versions of NOS 6SN7's, I still have several NOS Telefunken E88CC(6922) and ECC83(12AX7) tubes that have been used in five CAT preamps over more than a dozen years. Those tubes still test like new. The Sovtek's and Electro Harmonix that came with my first CAT didn't last 1500 hours. Yah, I know, we're talking 6SN7's but I'm guessing any good NOS will last waaay longer than anything produced today. Some of those old 6SN7's were rated for 10,000 hours!