Jack with external and internal audio interfaces

[Mac]

Hi,

When I start Jack with my firewire device the I/O's of the onboard audio
disappear and only the 10 I/O's of the firewire device show in the
connection list.

If I start audacious and tell it to output to Jack, then two more
outputs show in jack and can be routed to the firewire outputs.

Is there a way to tell the onboard I/O's (headphones, mic, etc) that is
(I'm guessing here) under the control of Alsa to direct these to Jack?

Regards,
Mac