Need help with graphics card before I buy my new gaming rig.

[Sporky0]

So basically I have posted a few times with multiple specs and have learned a lot about what is good and I feel a lot more confident in my ability and understanding of building a decent rig.

The spec I have managed to dwindle it down to is this:

Case
PCS MAELSTROM T900 BLACK GAMING CASE (£59)
Processor (CPU)
AMD PHENOM II X4 955 (3.20GHz/8MB CACHE/AM3) - BLACK EDITION
Motherboard
ASUS® M4N98TD EVO: DDR3, 2-Way SLI, SATA 3.0GB/s
Memory (RAM)
4GB SAMSUNG DDR3 DUAL-DDR3 1333MHz (2 X 2GB)
Graphics Card
1GB NVIDIA GEFORCE GTX465 GDDR5 PCI EXPRESS - DirectX® 11
Free Item
FREE MAFIA II Game (RRP: £34.99) with a qualifying GTX 4xx Series GPU!
Memory - 1st Hard Disk
1TB WD CAVIAR GREEN WD10EARS, SATA 3 Gb/s, 64MB CACHE
1st DVD/BLU-RAY Drive
24x DUAL LAYER DVD WRITER ±R/±RW/RAM
Memory Card Reader
INTERNAL 52 IN 1 CARD READER (READS XD, MS, CF, SD, etc)
Power Supply & Case Cooling
CORSAIR 650W PSU (TX650) 80+ ULTRA QUIET (£76)
Processor Cooling
STANDARD AMD CPU COOLER
Sound Card
ONBOARD 8 CHANNEL (7.1) HIGH DEF AUDIO (AS STANDARD)
Network Facilities
ONBOARD 10/100/1000 GIGABIT LAN PORT
USB Options
6 x USB 2.0 PORTS @ BACK PANEL (MIN 2 FRONT PORTS) AS STANDARD
Operating System
Genuine Windows 7 Home Premium 64 Bit - inc DVD & Licence (£79)
Office Software
FREE Microsoft® Office Starter 2010 (Limited functionality Word & Excel)
Anti-Virus
NO ANTI-VIRUS SOFTWARE
Warranty
3 Year Standard Warranty (1 Month Collect & Return, 1 Year Parts, 3 Year Labour)
Delivery
STANDARD INSURED DELIVERY TO UK MAINLAND (MON-FRI)
Build Time
Standard Build - Approximately 9 to 12 working days
Quantity
1

Price: £780.00 including VAT and delivery.

Now I have nothing against this spec and it's looking like it is going to win me over and it is probably what I will be buying.
However, I have been looking at other configurations to see where I could save some money to improve one bit or take out something unnecessary. The bit that keeps getting to me is graphics cards. I have had people telling me what graphics card I should get or shouldn't get, but it hasn't really helped me understand why I should get said graphics card when I can get a cheaper graphics card that to me seems to be of equal power.

The graphics card in question is the Nvidia GTX465 which I have chosen on the above spec. Now I don't know the difference between one graphics card and another very well, hell I can't even tell the difference between ATI and Nvidia they're both the same to me.
Thing is I seem to be able to save myself a lot of money by having an ATI card rather than an Nvidia card. The amount of money I can save is like £70!
People have told me that the amount of cores that the graphics card has is a good way to tell it's worth. which is why many people have said that the Nvidia GTX465 is better than the GTX460 which I understand fully appreciate. Looking at the details of the following 2 ATI cards it seems to me that they have more cores, now I could be wrong because the Nvidia details says "CUDA cores" and I have no knowledge of the difference if there is any. So help would be appreciated.
This is what I'm struggling to understand:
Price with an Nvidia GTX465: £780
Price with an ATI 5770: £711
Price with an ATI 5830: £762

would having any of these ATI cards really be such a downgrade to the 465? I have no problem buying the 465, but if there is a way of saving any money at all without sacrificing a huge amount of performance then in my books the saving of money would outweigh the loss of performance (the exact ratio as to which this is acceptable I do not know but with any responses I will be able to better figure this out).

Saving that money would actually better allow me to get a second graphics card in the future and also upgrade something else in the spec. Or for only £1 more I could have 2x ATI 5750, which is a lower model than the previous 2 cards I talked about but surely two of those cards would out perform 1x Nvidia 465?

Any light shed on this would be much appreciated because I would really like to be buying my new rig very soon but I want to be 100% sure that I'm getting The most for my money and still receiving exactly what I want.

Cheers, Sporky0

[Phoenix]

The GTX465 is a lot better than the Radeon 5770 however the difference between the 465 and 5830 isn't as great and in some cases the 5830 actually performs better (Left 4 Dead, 1920x1200 resolution, maximum quality, 8xAA/16xAF). In other games such as DiRT 2 (1920x1200, High Quality, 4xAA) the 465 will give you 6 more frames per second and in Crysis: Warhead (1920x1200, Frost Bench, Gamer Quality + Enthusiast Shaders, 4xAA) you'll get an additional 7 frames per second. The 465 will give you better performance in most games and has the added utility of having CUDA technology for photoshop (and other software) but the 5830 isn't a bad choice either as it will allow you to play all modern games at high settings if you'd prefer to save the money.

[PCS]

What games do you play sporky? The extra £70 is only worth spending if you want the best possible gaming experience for your money. If you're happy playing on medium/medium high settings and having a slightly less future proof card, the HD5770 is great. It's a very popular card and offers great "bang for buck".

[Meds]

On paper, the GTX465 is the best graphics card in terms of performance and if you can squeeze this into your budget then I would recommend to do so.

One thing I would steer you away from is ordering two "inferior" GPUs in Sli/Crossfire now. This would not only limit any future upgrades, I very much doubt it would even improve performance much more than ordering a single, more powerful GPU.

[Sleinous]

One thing I would steer you away from is ordering two "inferior" GPUs in Sli/Crossfire now. This would not only limit any future upgrades, I very much doubt it would even improve performance much more than ordering a single, more powerful GPU.

101% agreeing with this

+You can THEN add a second of the better GPU you bought in say a years time and be left with an SLI config twice as powerful than the SLI config you could have bought right at the beginning.