For what it's worth, I'm using Force 10 speed levers with Dura Ace 7800 brakes and they work perfectly - at least it sure feels that way to me.
If you look on ebay, there's always lots of Sram RDs up for sale, various lines, various colors. I don't think you'll have any trouble finding a nice condition Force 10 speed for $30-40 fairly quickly, less of course for Rival and Apex. Just went through that process to match the above levers.