Thanks guys. It sounds like the Gigabyte is a winner then.
In terms of whether or not to go with Nvidia and talking about mantle etc. I realise that its quite hard to know what games will be supported. Really I will be playing DayZ quite a lot and GTA5 when and if it comes out on PC.
If there is a similar performance between the GTX 780 and R9 290 then the cheapest would be best for me. I will take a look at the 780 prices again first.
Thanks again
EDIT: I have just read your edit above, this is one of the things that worries me. I have never had an Nvidia card and I always feel that I'm missing out on the quality/better feature set. This may be completely wrong so apologies if this is.