While you are not completly out of luck with this setup, you are going to have to "rig" this to work. I do not recommend this solution but it should work. The only way I can see to get this setup to run would be to purchase 2 line level converters (commonly used in car audio, available at circuitcity, bestbuy, etc). Plug them into the front channel and rear channel outputs of your Sony receiver. Make sure you turn off the subwoofer and center channel in the setup menus. You will then need to get a pair of stereo rca male to stereo 1/8 minijack female adapters and plug them into the line level converters. Plug your Klipsch speakers into these adapters and you should have sucess.
I DO NOT recommend this solution. You are probably better off buying speakers designed for this application as opposed trying to rig computer speakers to work. This should get the job done but I wouldn't do it.