@ sycophant - Surely with all that hardware, there’s one or more free copies of Cubase LE OEM laying around, which also includes VST System Link to start experimenting with If you decide VST System Link works great for you, but you want/need more capabilities than what the freebee does, you can then use/buy a capable older/newer full version
Another free/cheap option with any capable DAW software…is simple audio midi networking between each computers audio/midi interfaces…all it takes is ONE midi cable out of Master machine into Slave, and ONE stereo audio connection out of Slave back into Master…and a whole lot of routing.