How much is my customised computer worth?

[Evan]

Hi,
I have just finished upgrading my Dell inspiron 530s, and am trying to get an idea of its value,

Here are the specs:
Intel Core 2 Quad Q9550 QGPK Yorkfield 2.833GHz 12MB 1333MHz
8gb DDR2 Ram
blu ray disc drive/writer, 14x speed
Ati radeon hd 3870 gpu
3tb Harddrive
USB 3.0
200 CFM Semi-silent case fan
580w Power supply with its own cooling unit
2x 300gb Harddrive

So, any ideas on price????

Thanks in advance.
Forgot to add, it's running Windows 8 pro 64-bit.