[thedanbob]

I actually encountered just this sort of setup recently: a Linux PC with a real-time kernel running JACK and Ardour, connected to an 18x20 USB interface. It was part of a live translation setup that was routing English audio to up to four translators, receiving their foreign language audio, sending it to IR headsets, and recording everything with Ardour.

Unfortunately, it didn't work very well; I tentatively put the blame on JACK but some other part of the system could have been interfering, or maybe the PC itself just wasn't powerful enough. I didn't have time to troubleshoot properly so I just substituted in my MBA running Reaper, ironically.