Ah, so the layout is:
Cartridge > SUT > passive (Sondex?) > phonostage > power amp.
Is that correct? ,If so it is not what I was thinking, and IMO not a good idea for two reasons:
[1] the phono stage is running flat out into the power amp and hence the signal to noise ratio will be poor for low settings of the passive volume control,
[2] the loading of the secondary winding of the SUT will vary with the setting of the volume control, and so too will the load impedance as seen by cartridge. This could affect the tonal balance of the cartridge and make it dependant on volume control setting, though the effect might only be small.
But as the noise/hiss is only noticeable if you put your ear directly up against the speaker, and you like the sound ("Sounds different and very good ... "), then I wouldn't worry.