I don't dislike Nvidia, I was very close to buying one, I just think that in his price range the Radeon is a better choice. There would not be any advantage to him having an AMD (Ati) card with his AMD processor. Let us not forget that you yourself mentioned that the image quality was worse on the Radeons, but the tests in the link show otherwise. You also said that the Radeon does not have DX11 Tesselation, which was again wrong. So you're pulling things out of an imaginary hat.
Both card companies have a few things that they will do better, different situations where one card company will outdo the other, but generally side by side the cards (HD6970 vs GTX570 for example) are relatively equal, so unless you specifically want to play a game where one card considerably outperforms the other the main factor should be price.
The fact is you can't go wrong with either card company.
As for the PhysX, there are only a very small list of games that use it, and to get the most out of it you really need to have a second card that takes care of the PhysX side of things. I have also heard of people running a Radeon for graphics and having an Nvidia card taking care of the PhysX.. Hell, that sounds hard to believe even on my side, I'd love to learn more about it.
I'm telling you what I've heard. I told you, my last ATI card was years ago. I think it wasn't even DX 9. But I'm not sure. As for Tesselation I've searched maybe half an year ago at the ATI site to see if they have it and I didn't found it. The only thing that I'm sure about is that the ATI cards have a bad let's call it "mapping" because I don't know how is it called in English. If you compare 2 cards (ATI & Nvidia of course) you'll see that the ATI has a LOT more than the Nvidia at the hardware side but they're quite equal on their performance. This means that the Nvidia card uses it's "power" in a better way.
As for PhysX, I already told that it's just a few games. Actually the only game that I play and has PhysX is Mafia 2. It's just incredible! But of course the game looks very good without it too. I've heard too that you can put a Nvidia card for PhysX when you have an ATI but I've read a few topics over the past month that with the latest drivers you actually can't. I don't know if it's lies, you have an ATI card and you should try. For PhysX card by the way, you can get a very small card for 50-100$ which will do alright. And the 500 GTX Series I think will do OK without PhysX card and with PhysX on "High".
You by the way said that a GTX 570 and a HD6970 will be equal. But when you're talking about the BEST card out there, Nvidia has it and actually your post kind of proves it. GTX 580/590 are just an era ahead. Which makes them cost as much as 1 used car in a good condition but this proves it that Nvidia can make better cards. The problem is that they put too high prices. It's like Intel vs AMD. Intel are maybe not 1 but 2 eras' ahead of AMD but the price of their processors is just insane. Of course if you want better quality you'll buy an Intel but for a casual user is always better to get an AMD. I'm usually an Intel fan but we were making a computer for my aunt and just because I know she won't have what to do to use the full potential of it, I choose an AMD just because it was cheaper. Of course Integrated video card went there too but I'd probably go with an ATI if I had to buy one again just because it's cheaper. Doesn't matter. I went to her this summer and as for the computer you can really notice the difference between an AMD and Intel. The AMD is 2x2,6 GHz if I remember well and it's just a lot lower in terms of performance from my old PC which was with 2x1,8GHz Intel. There were just lag spikes and s**ts. It's just not good enough. (we're not talking about games here..). So as for the ATI/Nvidia battle, it's quite the same. ATI gives better prices on their High End cards (without counting my country
) and that's what gets most people frustrated and that's why many people hate Nvidia. They ARE overrating theirselves. That's the thing I don't like about Nvidia. As for ATI, they're the newer brand when it comes down to making GPU's. (As far as I know.. Nvidia are from 1993 and ATI makes video cards from 1995). This probably makes them put higher prices. They may be thinking that there's still no one else in the business.
So.. He has £200. Here are his choices:
2GB Cards:
GTX 560 Ti 2GB: Just £14 over what he has which I don't think will be a problem..
http://www.ebay.co.uk/itm/Palit-Nvi...raphics_Video_TV_Cards_TW&hash=item5ae33e4756
ATI Radeon HD 6950: Just £9 over what he has which I think won't be a problem..
http://www.ebay.co.uk/itm/VTX3D-AMD...raphics_Video_TV_Cards_TW&hash=item1e6704f352
1GB Cards:
Firstly from Ebay:
GTX 560 Ti.
http://www.ebay.co.uk/itm/Asus-Gefo...raphics_Video_TV_Cards_TW&hash=item20bddec47b
HD6950
http://www.ebay.co.uk/itm/Asus-ATI-...raphics_Video_TV_Cards_TW&hash=item20be172bc6
Amazon:
GTX 560 Ti:
http://www.amazon.co.uk/Asus-GeForc...R8DA/ref=sr_1_2?ie=UTF8&qid=1320152144&sr=8-2
HD6950:
http://www.amazon.co.uk/XFX-Radeon-...5AT0/ref=sr_1_3?ie=UTF8&qid=1320152174&sr=8-3
Now you should know that the ATI uses more PSU power. I don't know if your 550W PSU will work with even 1 of them but this is written in the Nvidia site:
Minimum System Power Requirement: 500(W)
I don't know on what kind of system they suggest these 500W.. That's the problem..
The same is written in the ATI site:
500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended
The ATI card uses 200W, the Nvidia uses 170W. 30W won't probably make a difference but if your PSU will be on the limit, it may prevent some unlikely PC turning offs.
Oh and by the way, each game is made for Nvidia OR ATI. It will run on both but it will always run better on one of them. I don't know about F1 2010/11 but you should check some benchmarks on the games you're planning to play. And by the way, on what resolution you're going to play on?
You should also check this site:
http://extreme.outervision.com/psucalculatorlite.jsp
Note that 4 cores CPU is still 1 physical CPU!
And as Ryan said.
You can't go wrong with either card companies. You can see 2 cards, same prices, same performance. One has MSAA the other has PhysX. You should maybe choose them by their color!
Red vs Green!
(That was a joke of course..)