Using headphone out to hook an alarm clock app to speakers

I own an Archos 43 Internet Tablet running Android 2.2, and I am looking either for an application or configuration option to allow using the headphone out port (if it is plugged in) for the alarm in an alarm clock app. I'd like to hook my Android device to external speakers in order to make the alarm louder than the device's internal speaker is capable of reaching. The ability to use the math alarm option would be nice, as well. I've tried the integrated alarm clock, as well as the free version of "Alarm Clock Plus". Neither of them seem to output the sound to the headphone port in their current configurations. I am not opposed to spending money if I know that it will work as a viable solution. Any feedback or solutions?