In regards to future proofing, I think you're right - but I guess how long a computer lasts for really depends on its intended purpose. For advanced gaming you're definitely right, you'll be doing very well to get 5 years out of a gaming rig. However for home/family/office use, 5 years would be considered a minimum. That's why I'm not expecting too much from this rig. I'll be using it for games for the first 2-3 years, after which I'll use it for office use or just for home streaming.
When in a few years I have a better idea of what's going on in my life - now that's when I'll invest more serious cash into a build.
Also, after my post yesterday I did a lot more reading about CPU's. Considering that you'd be using a dedicated graphics card, with lots of processing power - would you really need an APU, or even an intel i series CPU? I've come to understand that the i series of CPU's have good integrated graphics capability - is that something that you would really need? Would it not be better to get a cheaper, but still as powerful AMD processor just to benefit from the processing power?
I think that's probably my final build decided then. Thanks for your help everyone. I'll probably order it next week so if you have any alternative suggestions please shout.
What I was saying about the apu was an example. Please don't get one. Intel 5/7 series are known for reliability and power. Switchin from intel to AMD completely changes your whole build so pick which!