Hold on to your graphic card for a few more months if you can. Nvidia is reportedly working on another GK110 based gpu for the summer.
"Similar in specifications to the fabled Quadro K6000, the new SKU could feature 13 out of 15 streaming multiprocessors on the GK110 silicon, working out to 2,496 CUDA cores, 208 texture memory units, a 320-bit wide GDDR5 memory interface holding 5 GB of memory, and 40 ROPs. Given that there's a deep ravine between the ~$450 GeForce GTX 680 and ~$1000 GTX Titan, NVIDIA could pick a price-point in the middle. The report claims the new SKU could launch some time between July and August, 2013." -[Source: techpowerup]

So while upgrading to a 680 might seem like the best thing to do about now, If I were you, I would probably wait and see how good the newer gk110 based gpu would perform at performance/price ratio, unless you have direst need for a new card. Besides, processing power nearly doubles with every new x00 series and gtx 6xx has been out for a year now. IMHO, it's not worth the upgrade, but I'll leave you to your best judgement.