An i7 makes no real difference compared to an i5 for gaming, unless you run at stock clocks. The 780 is aimed at people who run at very high resolution or don't care what they pay for a graphics card. Spending >£500 on a graphics card for 1080p gaming, with a budget of £1,300 is not a good idea in my view.
Add in a soundcard and an SSD and delivery costs and the price is more like £1,650.
Add in a soundcard and an SSD and delivery costs and the price is more like £1,650.