Considering the signal levels coming out of a cartridge -- even a MM one which is high compared to MC -- I'd opt for a small phono preamp and feed its output to one of the auxiliary inputs. You might look at something like the Schiit Mani (only $130). It has a single stereo phono input, adjustable for MM or MC, several levels of amplification, and a single stereo line-level output.
Now you're set:
Now you're set:
- Phono 1 for TT 1
- Phono 2 for TT 2, and
- Aux 1 for TT 3