I too have super sensitive Avantgardes (107 dB Duo Omegas) and run a tube pre and tube amps (as well as an AMR tube CD player, and analog with tube phono stage) with virtually zero noise - one must put their ear right up to the tweeter horn to hear the slightest hint of tube rush with no music playing, even at "generous" volume settings.
I would definitely check for ground loops first, and ensure that you have clean power (I run dedicated 20A circuit for my amps/sub amps and dedicated 15A circuit for my pre and sources, the latter through a Shunyata Hydra).
A tube pre with separate L&R gain controls will allow you to dial in the sweet spot of gain for your rig, as well as providing a de facto balance control, handy in asymmetrical rooms.
I would definitely check for ground loops first, and ensure that you have clean power (I run dedicated 20A circuit for my amps/sub amps and dedicated 15A circuit for my pre and sources, the latter through a Shunyata Hydra).
A tube pre with separate L&R gain controls will allow you to dial in the sweet spot of gain for your rig, as well as providing a de facto balance control, handy in asymmetrical rooms.