I would personally start with an i5 2500, not that much dearer than an i3 but a good bit better, an i& would be awesome but probably a bit OTT for your uses. 
  
Then basically you know the score, as good a motherboard as you can afford, as much ram, and as good a graphics car....  
  
I would suggest going to a website that make us the system for you, doesn't cost you much more and gives you piece of mind  
  
Oh and Graham I am working (honest I am)