Please help - Firstmix i/o & Cross DJ LE2.6.0

Hi there,
I've read some of the topics and followed the suggestions on how to resolve the issue of the sound not "being able to split between the speakers & headphones" without any success.
I'm using a PC with Windows 8 and 2 sound cards. I've got the earphones in the jack in the front of the decks and the RCA cable is plugged into the Line In on my default sound card. I've change the settings and made the default device to be the FirstMix I/O Master Out Put but still nothing.
I've tried connecting the decks directly to a set of speakers using the RCA cables but still no split of the sound.
I'm obviously doing something wrong but just don't know what else to do. Any advice or suggestions will be greatly appreciated.
Thank you.
I've read some of the topics and followed the suggestions on how to resolve the issue of the sound not "being able to split between the speakers & headphones" without any success.
I'm using a PC with Windows 8 and 2 sound cards. I've got the earphones in the jack in the front of the decks and the RCA cable is plugged into the Line In on my default sound card. I've change the settings and made the default device to be the FirstMix I/O Master Out Put but still nothing.
I've tried connecting the decks directly to a set of speakers using the RCA cables but still no split of the sound.
I'm obviously doing something wrong but just don't know what else to do. Any advice or suggestions will be greatly appreciated.
Thank you.