If that, I've had my Quad Core version of that 6 years and if you depreciate it by 25% a year it's worth £177.98£150 prolly, you dont mention psu make, brand of ram, and size of hdd and name of case, it might nudge the price a little either way.
This, if you can be bothered that is because if you don't sell all the parts as spares on ebay you'll have less money and half a box.sometimes you find its better to split the system up, but then the only that prolly wont sell is the case most of the time