Provided there is such a connector on the board (note I am not seeing any mention of this in the board's TPS document) and there is an SPDIF input on the particular GTX295 card that you have, you could use it to inject audio into the HDMI (or DP) stream (this is it's purpose, after all).
If the connector is not present on either side, there is another alternative to consider. You can get adapters that take in a DVI (or HDMI without audio) video input and a separate audio input (from the back panel of the motherboard, for example) and then output a full HDMI with audio signal. Here is a link to one such adapter: Amazon.com: Monoprice 108124 DVI and R/L Audio to HDMI Converter.
Hope this helps,