I was reading this thread:
HOW TO: Get sound from PC to Car Stereo / Amp

im planning a setup right now, and it calls for two amps and no HU. The Sound card i want to use is a USB sound card. It is NOT a 5.1 and only has stereo outputs. Now according to the thread above i could use a splitter and split that stereo out into the 4-channel amp. But i was wondering where i could get sound from for my mono amp for my sub? Should i split the wire going to the rear speakers again and put one into the sub amp and the other into the rear set of speakers for the 4-channel amp? or is there another method?

I was reading another thread and found this: http://www.rolandus.com/products/pro...3&ParentId=114 to be the alternative to a sb audigy usb card but on the same note the sb audigy can be 5.1 and easily setup. Hence why im trying to see if its feasible to manage 4.1 out of a single stereo output without losing too much quality?