Passive Preamps w/ Transformer Volume Control

Well, you could also consider diyhifisupply's django or MFA (I think) using Stevens & Billington trannies.

However, I'm not sure what you'll gain by adding an inductive volume control to the system -- other than source switching capability.
Are you unsatisfied with yr present direct set-up?

Thanks for the clarification Edwyun.
In fact, I'm using a S&B passive. I prefer this to a ladder type resistor based unit -- which, OTOH is cheap to make (the S&B TVC is expensive); Both of the above where better than the basic rotary switch equivalent; I preferred relay switching than the mechanical, rotary, counterpart.