can speech output be different from default output

[Neighmist]

Is there a way to set the leopard system voice (Alex), to goto USB speakers, without changing the default sound output from built in audio. I'd like to hear those "Announce when alerts are displayed" and "Announce when an application requires your attention" alerts on my USB speakers, because I can feel confident the USB speakers I bought just for alerts, will never be turned down or muted.