I have 2 GTX680s (2GB) purchased at/near launch day a few years back. One was a reference 680, the other was a SC clocked model. Both are EVGA brand, and both are bios modded to SC levels, with identical clocks for parity in SLI mode. They weren't the best over clockers when paired (one held the other back) so I settled for what I knew was stable have had zero issues. Both cards are also fitted with XSPC razor waterblocks. (http://www.xs-pc.com/waterblocks-gpu/razor-gtx680-new-style) These cards rarely see above 40c. Debating selling them and upgrading to something a bit more current. Just curious what ballpark i should expect to be able to sell these in.
Depending on the prices in your country, id guess around 250... but im guessing more people would be interested, if you fitted the original air coolers (if you still have them), as very few uses custom loops (especially amongst those that would be interested in 2 year old used Cards).
Unfortunate, but what Dorlor said is true. I'm also guessing you might get more by putting the original cooler back on and selling the blocks separately.
I had a hell of a time selling 2 680 ftw 4gb. They took 6 weeks to sell and I got 300 and 250 usd for them. Sell em on ebay otherwise I would guess 200 each if you stick the air coolers on em and sell them here.