How much is my computer worth?

I'm thinking about selling my Lenovo IdeaPad Y580 laptop, specs;
Intel Core i7-3610QM CPU @ 2.30GHz
RAM 8GB
GeForce GTX 660M + integrated Intel graphics
Windows 7 Home Premium 64bit SP1
654Gb HDD + 24.4 HDD
Webcam
Full HD Display
2 USB 3.0 and 2.0 ports
SD Card reader
CD/DVD RW Reader
Headphones, Mic Jack
Working Battery and Power Supply Cable
Ethernet port
HDMI port