No you dont need an sli board, your board will work. No, you dont need an Sli bridge.
After you install the card simply go into the Nvidia control panel, go to the sli and physx configuration and select the 560 ti and check dedicate to physx.
Assuming that your nvidia drivers are up to date that is all you have to do. If not then update to the newest driver then do the above. Reason being that the 560 ti didnt share drivers with other 500 series cards for a little while.