Will a single 6 pin power connector handle the gtx 560 ?

yep right ... you need 2x 6pin pcie or like this
pcie6.jpg

remember you had limited power for it
 
http://www.newegg.com/Product/Product.aspx?Item=N82E16812267004
http://www.newegg.com/Product/Product.aspx?Item=N82E16812887001

The GTX 560 video card reqwuires two 6 pin power cables to work , the links above show what cables will most likely come with the card and you can take one of them to make the second 6 pin connector. There is also a splitter cable that you can get to make two connectors out of one.

http://www.newegg.com/Product/Product.aspx?Item=N82E16812200935

You may not be able to buy from Newegg but the links are for your reference to see what you need.
If you can aford it you could buy a power supply with two 6 pin connectors or if not you can use the adaptors.