The processor is good but the weak point of most off the shelf systems is usually the videocard. The GTX760 is a good mid-range card and will probably play most games on mid to high settings and you'll be quite happy with it for now. But as you can see here, simply upgrading to a GTX970 with the same CPU will net you nearly
double the benchmark and double the performance for only $160 more, by far the biggest bang for the buck in any gaming purchase. The means higher settings, likely maxed out on every game, and the ability to run triples with high settings as well in most games, something you won't likely do with the 760.
In short, I'd buy the best video card you can afford and build my system around it. At that particular store if you spend another 200pounds or so you can get an i7 + the GTX970, double the system for only a couple hundred more. If you can't afford it then the 760 is still a good system, but if you can afford it get the better system and it'll last you much longer and you'll be much happier in the long run with it's performance.