I've been amp curious for a very long time.
Recently I've been interested in some of the lower power pentodes that are also meant to be easy to drive, like the EL95 and EL84. If amps based on these tubes are designed properly there's not an SET made that can keep up by any metric audiophiles value. They really can work quite well!
One hero in this department is the Dynaco ST35. Its inexpensive, compact, and if properly refurbished, very musical. I recently rebuilt one with new filter caps, new RCA connectors, and set it up to prevent ground loops with a grounded AC power cord. If you have speakers that don't need a lot of power this amp is surprisingly neutral and musical.
I've also had an interest in some of the Electro Voice amps from the mid and late 1950s. These used a Circlotron output similar to what we've been using in our OTLs for the last 47 years.