It's only worth what someone is willing to pay. It's hard to put a set price on custom builds because no two are exactly alike. But a shot in the dark I'd say in the ballpark of $300 (USD assuming you are in the US). No overclocking ability, and only one stick of 8GB memory (making it more expensive for someone wanting a 16GB upgrade and needing to buy a 2x8GB DDR3 kit). Your video card is the single most valuable component. I see 4GB 960s selling on eBay for between $150-$180.
You might get more money parting it out (generally a CPU and motherboard combo sell pretty well together on the used market). However, doing that has risks as well. You may be stuck with some components that don't sell. Of course this all depends on where you...