I’ve used 6SN7 preamps for years now. Richer tone, greater linearity, in general less gain, and better availability of new production tubes that actually sound good. While I usually run NOS tubes, there are currently produced 6SN7s that I could easily live with if the supply of reasonably priced NOS tubes dried up.
My latest is the Atma-Sphere MP-3, possibly The Final Preamp for me. I’ve also owned a Don Sachs Model 2, the Modwright LS-100, the LTA MZ2, a Consonance Cyber 222, and a Wright Sound WLA12A.