The tape out can feed another integrated amplifier, the volume control of the Scott (or any amp for that matter) does not affect the output of the signal of the tape out. Even if the Scott is off, the tape out will provide the signal to the next amp..
No speakers connected to the Scott Amp ?...this is safe as long as you have a speaker off switch in the amp, this internally connects a dummy load to the amplifier. Another option is to connect resistors in the loudspeaker connection to provide such a load...
Want to use it as a pre-amp ?...try connecting the headphone output of your Scott to your desired power amp...I tried it and it works with negligible (to me none at all, some will say meron) loss of dynamics. This would enable your Scott to work Like a Pre-amp......BTW...if your Scott has headphone jacks...it should have a speaker off switch....done this before, when I had the Dynaco ST70 II
Another option is to have a certified tech create a pre-amp output for your Scott, my Scott 299d has a built in Pre-out ...buts its mono, I use it to provide signal to my subs so okay lang....if your Scott has such output, i guess it would be easy to separate the left and right signals...