Thanks for all your replies, much appreciated. Reaperdeeper: Thanks, that sounds like the most sensible way, really. It's a shame that I'd have to sacrifice the 1st PC's SPDIF inputs in order to monitor from the 2nd PC, but there we go. Come to think of it, If I did need to monitor the two PCs simultaneously I could sum their outputs with a small mixer, as mentioned in my first post. A rather clumsy approach, but there if needed! After tracking in the second PC, I'd be needing to export the files as individual tracks into the 1st PC's project, so after the initial tracking, there'd be no need for the 2nd PC really (unless I needed to record a 2nd batch of 24 simultaneous tracks...!) Again, I'm very grateful for the advice here, and I look forward to trying it out! Aled