GTX 570 idle temps too high?

I don't think replacing it could lower the temperature; you probably have a ventilation problem. What are your full specs? Can you post a picture of your case/ventilation setup?

http://i.imgur.com/xzhT9.jpg

There's my set-up, here's my case.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

The top fan is blowing out, side fan is blowing in, and CPU fans are blowing in, through that radiator. So hot air is coming in from the CPU fans.

EDIT: Even if I remove my second card the temps are still high.

Did you clean heatsink, fan? My geforce 6800xt 512mb reach up to 96c while gaming and idle 70. I cleaned it and now idle 30 full load 50

Did you clean heatsink, fan? My geforce 6800xt 512mb reach up to 96c while gaming and idle 70. I cleaned it and now idle 30 full load 50

The radiator should absolutely be blowing out. That way it'll serve as an exhaust for the rest of the case and cool the CPU at the same time. I wouldn't be at all surprised if that were to solve the problem.

It has also been found that fans attached to side windows will create too much turbulence inside a case and make cards overheat.

that radiator should be exhausting air not blowing it in to the case. Other than that you're case/setup shouldnt have anything to do with it. Make sure you have EVGA Precision and set up the fan control so that you have a linear speed increase from about 50% @ 30 degrees to 100% at 85 degrees. Also, you're card should clock down to about 400Mhz then down to about 50Mhz when it's idle. Note that the card will not clock down and will stay in its P0 power state when you have multiple monitors connected and active. If you ever want it to get nice and cool, use Win+P (on windows) to enable/disable multiple monitors.
When idle, my 570 hovers between 36 and 40 degrees, when playing crysis 2 it gets up to 58, when playing BF3 it gets to 65