How do I hook up a subwoofer and a single 4 channel amp to an empeg? Two channels go to the front component speakers and the other two will be bridged for the sub. No rear speakers.

Best answer is to read this part of the faq:

http://www.riocar.org/modules.php?op=modload&name=FAQ&file=index&myfaq=yes&id_cat=3&categories=Car+installation+questions&faqent=159#159

It offers several ways to hook up a sub.

His question is simpler than what the FAQ covers. Sounds like he's saying he doesn't need six channels, he just needs four. So just do it: Four channels on the empeg go into four channels on the amplifier, and bridge the two rear channels on the amp for the sub.

Note that in order to do this, the amp must support bridging of the rear channels like that. That's up to the amp, not the empeg.