Windows 7: No Sound With SLi Setup

I bought a 2nd 580 3GB GPU fitted it in no probs, and apart from trying to figure out which DVI slot runs the display (for some reason it wasnt the original) - got SLi up and running. However the first thing I did was to benchmark it with the "Heaven" demo - it ran (with audio) and then spluttered and crashed.

Since then I have no sound on the PC... apart from via the TV
The PC is hooked up to a hi-fi usually via line-out 3.5mm jack. Since the upgrade this wont work at all. Sound only comes via the option of the TV in audio settings. Ive disabled that, and saw "speakers" were not plugged in (when they were). After much tooing and froing I googled this and found it may be a Realtek setting. I enabled "front ports" via Realtex and the speaker icon re-appeared, I tested the unit - NO SOUND!! However the green "level" bars show up for both back panel and front panel but nothing is heard. Ive tried a different set of speakers, different cable and different OS but same issue.
Ive tried uninstalling the Nvidia drivers thinking it could be their HD Definition Audio driver, also went into Nvidia control panel and saw an option for the GPUs audio to be turned off - still nothing. Tried disabling onboard audio via BIOS - still nothing.

Tested my hi-fi - works fine.

Its my worry that something may have borked up on the motherboard (Rampage 4 Extreme) so am turning to you for help ;-) it could be a settings issue Ive missed but for the life of me cant find it.

A clue may be in device manager HD Definition Audio appears 8 times. Ive removed them but still no solution.

Also checked for loose cables inside the PC and all are tight.

[Solved] GTX 295, No audio over DVI to HDMI - Nvidia - Graphic-Displays