Not a whole lot. Pricing the parts on Newegg (ignoring the monitor, keyboard and mouse) gets a new price of about $800. Since you're not a professional builder (no warranty) and you overclocked (added wear and tear on the parts), knock off 25% of that. Then take off 10% ($60) for every couple of months of use. I'd say getting $450-500 would be good. Of course, you didn't list the PSU, so if it's a decently sized, high quality one, you could probably increase that to $500-550.
You'd probably do better to part it out. I'd be surprised if the SSD, GPU, CPU, case and motherboard (with or without the OS) didn't go for more than what I've listed for the build.
I'll add that the amount you get changes a lot with who you're selling it to. If you're selling in a high tech knowlege group (like the Classifieds here at Tom's or any other computer/tech forum), you're going to get less. You're also likely to get less haggling over it, simply because people know what it's worth. If you sell it to the unwashed masses (eBay, Craiglist, etc.), you're likely to get more money for it, but you'll also end up with a bigger headache.
It's typically not advised to sell it on eBay, as you'll lose "profit" on the shipping and other fees. Craiglist is generally considered a better choice if possible.