Depending on the manufacturer, you may be able to load different firmware on the card. My Gigabyte Windforce GHz edition 7970 came with a stock voltage of 1.25V; with their "standard" firmware (instead of "GHz"), that went down to 1.17V which has helped with temps and actually gets me better hash rate since I use auto core clock control in cgminer to maintain constant temp.
Oh, and try Florida if you think you are struggling with temps ;-)
This is a grand idea. I'll do some research and see how this is done on Linux. I'll post back later with my results.