Good hardware, low FPS

Hi, I purchased my computer a few months ago and have upgrades it twice with a new video card and power supply, everything runs amazing, Skyrim, Battlefield 3, Max Payne 3, L.A. Noire, Rage, Witcher 2, Mass Effect 3, Crysis 2, Civ 5, Arkham City and more ALL 60 FPS at a beautiful 1920x1080, yet darkness 2, warhammer space marine, Deus ex human revolution and saints row the third all hover at about 20 fps no matter the settings, just really frustrating that my gaming pc I have al least $1000 into already cant run a few, less hardware intensive games. I have all current drivers installed, so I'm literally at wits end here. Here are my specs:


Mainboard :Gigabyte M68MT-S2
Chipset :Family 15h Processor HyperTransport Configuration
Processor :AMD FX 4100 @ 3717MHz
Physical Memory :8192MB (2 x 4096 DDR3-SDRAM )
Video Card :NVIDIA GeForce GTX 560 Ti
Hard Disk :Seagate ST500DM0 02-1BC142 SCSI Disk Device (500GB)
DVD-Rom Drive :ATAPI iHAS124 B
DVD-Rom Drive :JKHSL TMNKLM70XAZ0
Monitor Type :E421VL - 42 inches
Network Card :NVIDIA nForce 10/100/1000 Mbps Ethernet
Operating System :Windows 7 Home Premium Home Edition Media Center 6.01.7601 Service Pack 1 (64-bit)
DirectX :Version 11.00
Windows Performance Index :5.9 on 7.9
Power Supply: Thermaltake 850w Black Widow
 
Please can anyone help? I don't mind spending the money to upgrade my hard drive if that's the problem, 500GB isn't enough for me anyway cause I'm thinking it's a memory problem but I don't know for sure, can't find much info on this.
 
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