Very low fps on dekaron using ASUS EAH6770?

this is an online game my brother plays and when he plays everything at max 1024x768 resolution when he and his party go up against a mob of monsters everything dropped at 1-5 fps -_- and to think this card could actually play crysis and other demanding games at 1440 resolution, i just played left for dead and played at max 1366x768(my monitor's natural max resolution) and saw at benchmarks it could play well even at 1920x1080 with decent fps, is there something wrong? by the way here are my specs:

CPU:AMD Athlon x4 640
Mobo:ECS-MCP61M-M3
RAM:2 x 4gb Kingston 1333Mhz
Monitor:AOC 1943W
PSU: Coolermaster Extreme Powerplus 500w
OS: I have dual-boot but used xp 64bit as my gaming OS

I have already downloaded the latest drivers at amd's site, the cd this GPU came with was awful, hence AMD is pretty well known for shady drivers but i never lost faith in them -__-

I just bought this card last week, said direct replacement can be done within the month and 1 year warranty provided,when i installed the card though i used AMD's site to download the drivers(automatically check and install one) then as curiosity struck i tried installing the drivers off the cd it came with then my pc actually slowed to a crawl when booting up, i checked GPU-Z and did dxdiag and when i used the drivers for the CD it identified the card as ASUS EAH6770 but when i used AMD's site drivers it showed a generic name instead of "ASUS EAH6770" it showed "Radeon 6700 Series", did i install the drivers right?will internet connection affect fps?what do you guys think?

While FPS in online games are at the mercy of your internet connection speed, you might want to look at your PSU. According to this review:
http://www.hardwaresecrets.com/art [...] iew/728/10

the Extreme Plus is not a good PSU. If your Graphics card is not getting enough power, it could be throttling the rest of your system.

but i am still wondering, because he gets great fps when in town, or fighting a few monster mobs but when he gets into the arena against monsters or with players that glow a lot and do AOE damages that's where the fps drops dramatically,is this still the influence of the internet connection when it comes to online games? ?_?