Look at the CFM (volume of air /minute) the higher the better. dBA - noise, the lower the better.
You can also get two bigger fans instead of 4 smaller ones.
This should be easy to mounthttp://www.newegg.com/Product/Product.aspx?Item=N82E16835200055
The air should move from the front of the cabinet towards the back around the receiver so you need slits or holes in the front to allow the air in.
This one is standardhttp://www.newegg.com/Product/Product.aspx?Item=N82E16835220036
LE: How are you going to power them?