2500$ System advice

A GTX275 can't handle your games!? GTX275 is a monster card...which resolution are you gaming at? My old, frail, week 8800GTS 640mb can max out most games on 1080p except for like crysis and others. Your 275 should be ripping through anything on 1080p and even higher.

The build you proposed though looks very good i'd say. Seems like you did your research, only thing is which brand of ram are you getting? And also, i'd save some money and not buy the 5970, keep the 275 and see how well it will scale on your build as it can very much be that your CPU is bottlenecking your videocard. If it's still bad, then get the 5970, or consider an nvidia GTX480.

I am using a 1080P screen, but I think the CPU is holding the PC back
I tried Dragon age and it was lagging on the highest setting, also aion in crowded areas

i think your cpu is holding you back. However if you were playing those games online, your ping might be laggin you. Measure how much fps you have in the game first.

At that budget....

$230 Antec 1200 w/ CP-850 http://www.newegg.com/Product/ComboDealDetails.aspx?Ite...
HAF 932 w/ Corsair HX850 would be an equivalent choice.

$520 ASUS P6X58D-E w/ Intel i7-930 http://www.newegg.com/Product/ComboDealDetails.aspx?Ite...
Better Board

$200 3 x 2GB Corsair DDR3-1600 CAS 7 http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Low profile heat sinks won't interfere with CPU cooler.

$85 Seagate Barracuda 7200.12 1TB http://www.newegg.com/Product/Product.aspx?Item=N82E168...

$100 CPU Cooler, fans, and doodads. See below

$25 Any DVD writer

$700 Twin Asus ENGTX470/2DI/1280MD5 GTX 470 (Fermi) http://www.newegg.com/Product/Product.aspx?Item=N82E168...
.....or
$640 Twin ASUS EAH5850 DIRECTCU/2DIS/1GD5 HD 5850 http://www.newegg.com/Product/Product.aspx?Item=N82E168...

$1800-$1860

Heat Sink - For performance and ease of installation, the Prolimatech Megahalems well fits both criteria. Mega w/ IC Diamond TIM and twin Scythe PWMfans . ($65 for the HS, $7 for TIM, $11 each for two PWM fans and $7 for a Y cable splitter).

http://www.frozencpu.com/products/8807/cpu-pro-01/Proli...
http://www.frozencpu.com/products/7038/thr-41/Innovatio...
http://www.frozencpu.com/products/10026/fan-639/Scythe_...
http://www.frozencpu.com/products/8418/cab-150/FrozenCP...

Pick one of the top 5 on one of these lists:
http://www.silentpcreview.com/Recommended_Heatsinks
http://www.frostytech.com/top5heatsinks.cfm#INTELHEATSI...
http://benchmarkreviews.com/index.php?option=com_conten...
http://benchmarkreviews.com/index.php?option=com_conten...

pick a TIM from the top few here:
http://www.hwreviewlabs.com/index.php?option=com_conten...
http://www.xbitlabs.com/articles/coolers/display/therma...
http://benchmarkreviews.com/index.php?option=com_conten...

Nice system, but I would add some remarks:
- you don't need 1000W unless you plan to go Xfire/XLI and OC. Maybe you can save some money - not much, though- and work on a higher efficency zone with your PSU if you reduce its power.
- if you can wait some 2 weeks, wait and see how Phenom II X6 perform and what's the price. It will hit the market tomorrow and early reviews should follow soon. Chances are that you can get 2 extra cores for free.
BTW, GTX 275 is still a great card.

Ok I decided to keep the GTX275
I have a Corsair TX 750 PSU will this be enough?

So I will buy these for the upgrade

6GB DDR3 3X2GB DDR3-1600

Intel Core i7-930 Bloomfield 2.8GHz

Gigabyte GA-X58A-UD7 or ASUS P6X58D-E

Western Digital Caviar Black 1TB

Cooler master Cosmos-S Full ATX case

Note : I am not from the US so I can't buy from newegg