Crysis problems

specs:
ASUS P7P55D-E Pro LGA 1156 Intel P55 SATA 6Gb/s USB 3.0 ATX Intel Motherboard62462751

Intel Core i5-750 Lynnfield 2.66GHz LGA 1156 95W Quad-Core Processor BX80605I575062462751 '

x2
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model F3-10666CL7D-4GBRH62462751

x2
EVGA 01G-P3-1371-TR GeForce GTX 460 (Fermi) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card62058386

Just by reading around I figured I'd be getting better then what I do. I can really only really be stable on directx 9 on my windows 7 64 bit on high setting at 1080p without AA. Even when I run it on dx10 on medium it gets pretty jittery. What could be he problem?