Excellent. I feared I was just making things worse and opening them up to more debate! I like how to stated "disabled Franco Di Santo", somehow insinuating that there's another type out there in the wild.
I'll be honest here and say that I'm not too clued up on building a system. I know about individual parts (mainly processors, RAM, graphics cards and hard drives) but other important components (like the cooling system) are beyond me. Plus, I'm not clued up on other imperative parts of the build, like compatibility and motherboards. Therefore my opinion should be taken with a pinch of salt.
Saying that though, I'm not too sure on the builds you're being given here. Firstly, you had recommendations before people even knew what you wanted/required. Sort of counter-intuitive. From what you've said you don't actually need a particularly monstrous PC so how people are managing to push your budget is a tad silly.
For example; I played the FM11 demo (and know for a fact it's really not that graphically intense), I play R:TW to this very day too (it's such an epic game and you win my respect for playing) and I also play SimCity3000. I do this on my laptop which has a
T9300 processor and
GeForce 8700M GT graphics card. Compare the stats on those to the stats on the stuff being recommended to you. I ran FM11 flawlessly, run with lag when battling in R:TW with highest unit size and large armies (about 15 units) with the battle set to triple speed and even the most modern SimCity could be easily handled by my laptop. Honestly, easily.
Beyond that, like you said, you have a PS3 for video games so your only real graphical concern is having an HD video card. My graphics card can do this. I feel this is the sort of realism that's not been mentioned yet!
I also use PS with minimal lag when dealing with large images. TV and movies we covered in the Graphics bit and music doesn't really matter much in this debate.
As for the newer TW's and Civ's, again, my PC can easily handle them. I don't think it'd manage to run them on the highest settings but mid-settings would run lag free I reckon.
I know I've sort of opened another can of worms up for you but hopefully this has put some things into perspective. You could easily achieve your aims be spending about £300, if that. From there you can build up. As long as you don't cheap out on the processor you'll be fine.
EDIT: Was quoting this post but doing so much that it took an age to post it up:
No no that actually makes perfect sense to me now and I absolutely love the analogy. What I have at the minute is probably a disabled franco di santo then.
Would you care to throw your hat in with a suggestion on which system would be best? Seems a good idea to get as many opinions as possible for such a big investment.