I loved my Air Tight ATM1 and now have the ATM3s. Haven't found an amp, nor am I looking to change....
The CJ MV50 sticks out as an amp which had the traditional el34 sound.
I have also used my JC Verider AudioBloc with EL34 and been very happy.
I would like to try a Lectron LH30 and Jadis Ja30 as well.