Caporegime
The 780 is rumoured to have a 30% performance gain over the 680 plus it's going to use the GK110 Kepler Architecture (this is what the Titan is based on) and will apparently have 5GB GDDR5 VRAM; so, essentially, the 780 is the "Titan LE". And if rumours of its price are correct (~$500 as suggested on techpowerup) then I will be very happy, although that seems slightly optimistic.
Yeah, if it is 30% faster than the GTX 680 then its only 10% to 15% slower than the GTX Titan
Some how i also think its not going to be half the price, i think we will be looking at a solid 600 Sterling.