How much would this imac be worth?

[realnumber 1]

My brother is selling his imac and I was wondering what you Apple experts think it would be worth?

It's in 100% perfect condition with all the boxes and everything and is about 2 years old. The reason he's selling is that he is a pro photographer and is getting an i7 imac to speed up his 36MP photo editing...

Spec is as follows:

21.5"
3.2GHz i3
16GB 1333mhz ddr3
ATI Radeon HD5670 512MB
1TB HDD
Wireless keyboard and Magic Mouse

Thanks in advance.

 

[Carlv8415]

About £999 New? S0 based on that about £600ish. Could be wrong....