headphones to tv

A year has passed since this advice appeared. Didn't need it then but I do now. Hope someone is still around to help.
I know some about computers...nothing about tvs and the new one i just bought raises the question asked a year ago. But I need, if possible, a more specific answer for my specific devices.
I just bought Vizio E420-A1 which has an analog output 3.5mm. The headphones I have now have RCA jacks... i.e. red and white plugs which I was able to plug directly into the analog audio outputs in the old TV. This Vizio has only that 3.5mm. I am expecting to buy Sennheiser rs120 headphones which I believe have RCA plugs too.
Would someone be able to check these two products and tell me which specific cable(s) I would need to plug the Senn into the Vizio without turning off the tv speakers.

http://store.vizio.com/e420ia1.html and http://en-us.sennheiser.com/wireless-headphones-stereo-rf-rs-120-ii

I really need to know and cannot find anyone who can give me the specific answer related to these specific products. Thanks!!!!!!!!!!!!