A couple of weeks ago I got an Audio Note P1SE -- the amplifier section of the Oto integrated minus the preamp section and am using it with my custom F120A fonkens, and with a little tube rolling they are the magic amp that these speakers wanted.
Tube rolling is a must IMO, as the stock EI tubes are a bit bright and harsh, and very much lacking in the bass department. I went through numerous combinations of new production and NOS output and driver tubes, and right now the magic combination is a pair of Telefunken ecc83 smooth plates and a quad of new production TAD EL84strs.
I almost bought an Oto a year or so ago but now the P1SE is giving me all that I need for a lot less money.
I'm not currently using a preamp, just my Havana DAC directly into the amp and it works very well.
HTH,
Jim