Is there a advantage to mounting a case fan in the side panel

I have two case fans. One in front (bottom) bringing in air, one in back (top) exausting air. I have a thermaltake ps which has two fans. If I mount a fan in the side panel overtop of the cpu will this disrupt the airflow I have now or will it help to mount it low in the side panel. I have read that this will not help temps but I see that some cases have a fan already mounted in the side. Thanks for any suggestions.

 

The fan on the side is there to help cool the video card.

 

cashys is right. i just built a new Athlon64 machine & the case i bought came with one. it does help a lot to expel the air. i'd get one.

 

Wow what a difference. I decided to put the side fan in, near the bottom just over my video cardwhere cashy suggested. At idle my temps were 40c to 41c and now they are 35c and 36c!! Room temp still the same. I really did not think it would make that much of a difference......Glad I did it. Thanks Cashy