Depends on your budget, main improvement with i7 is hyperthreading, double the amount of threads, more l3 cache, and a higher factory and turbo clock, but it comes at a hefty increase in price. It can improve video and editing in some scenarios, so it may be worth it if you plan to use the system for quite some time .
The Skylake platform was released a couple days ago, so you can consider that for your project as well. It would be interesting to play and present the latest technology, rather than a previous generation. You would have a system good for the next 3 years at least. There will be many future games, software, and hardware that will complement it extremely well.