Graphics card upgrade

I'm looking to upgrade my PC for higher performance in games. Currently I play games such as Starcraft 2, Mafia 2, World of Warcraft, Left 4 Dead 2. I might buy the new Call of Duty when it's released as well and play that.

These are my current specs:
CPU: AMD ATHLON II X4 620 2.6GHZ
Motherboard: GIGABYTE GA-M720-US3
Memory: CORSAIR DDR2 XMS2 PC6400 1024 MB x4
Graphics Card: ATi Radeon HD3850 512 mb
PSU: Zalman ZM600-HP, 600w

I'm thinking the graphics card is currently the weak link in my system and what I should look into upgrading, is this a correct assumption?

The card I have been looking at buying is XFX ATI Radeon 5850 1024MB HD-585X-ZNFA XFX ATI Radeon 5850 1024MB GDDR5 PCI-Express Graphics Card
It looks to me like it would be a good upgrade and the price tag fit my budget very well.
Any comments/suggestions on this? Would this be a good idea or should I look into upgrading something else instead? Also, will my PSU be enough with that graphics card?

Thanks in advance!

Darician said:

That's not a bad upgrade idea with the Radeon HD 5850. Another suggestion would be a GTX 460 if you can find the version with a 256-bit Memory Interface at a decent price. Either way, you'd be very satisfied with the performance you'd get.

How close are they performance wise? Looks like they have pretty much the same price tag.

How about my PSU, will it struggle to power the machine with a new graphics card? Link: Zalman ZM600-HP

Tervel said:

How about my PSU, will it struggle to power the machine with a new graphics card? Link: Zalman ZM600-HP

It'll be more than adequate. Four 12V rails, each rated at 16A. (The maximum total draw on the 12V lines is 504W, or 42A.)

Examples, with requirements:

EVGA | Products 400 Series Family&sw=

(450W, 24A at 12V)

SAPPHIRE- HOME

(500W)