Hi, pete23,
I use a Schitt SYS for a similar situation (shared preamp input between DVD player and second turntable) and having the volume control is actually quite handy for equalizing the signal strength between the two sources. I can run the SYS full range with the phono input and attenuate the high output of the DVD player so the amp is running at an optimal level. I otherwise use Harrison Labs and Rothwell inline attenuators to adjust signal output strength of the DAC, bridge/streamer, and CD player. I hear no meaningful difference between using the SYS volume control and the inline attenuators. The stereo system sounds better with the signal attenuation than no attenuation at all. (Probably a good case for using passive or low gain preamps.)
Regards,
Tom