Should be like £100 drop, so probably 100 EURO drop.
Should end up costing 400~ EURO, ~20-30% drop
You could get 2 144Hz monitors, one 780Ti would struggle, two would make it perfect.
Difference between 60Hz and 144Hz, the 144Hz will feel buttery smooth.
I'd suggest a high res screen tbh, it won't be buttery smooth, but it'll like looking out a window.