[Build Help]Rate the machine and help me organize an upgrade

Hey guys, so I built my current machine back in August 2011. These are the parts.

• ASUS P8Z68-V Pro Z68 LGA1155 ATX 3PCI-E16 2PCI-E1 2 PCI B3 Motherboard

• Intel Core i7 2600K Quad Core Unlocked Hyperthreading Processor LGA1155 3.4GHZ Sandy Bridge 8MB

• Noctua NH-D14 LGA1155/1156/1366/AM3 I7/I5/PHENOM Heatpipe Cooler W/ NF-P14 140MM & NF-P12 120MM Fan

• Intel 510 Series 120GB Solid State Drive SSD 2.5IN SATA 6GB/S Elm Crest

• Corsair Professional HX750W 750W ATX 12V 62A 24PIN ATX Modular Power Supply Active PFC 140MM Fan

• Western Digital Caviar Black 1TB SATA3 6GB/S 7200RPM 64MB Cache 3.5IN Dual Proc Hard Drive OEM

• Liteon DVDRW IHAS224-06 24X SATA Black With Lightscribe

• x2 G.SKILL Ripjaws X F3-12800CL9D-8GBXL 8GB 2X4GB DDR3-1600 CL9-9-9-24 Memory

• Cooler Master Haf 932 Advanced Full Tower EATX Case 7X5.25 2X3.5 5X3.5INT USB3.0 eSATA 1394 Black

• MSI GeForce GTX 580 Twin Frozr II OC 800MHZ 1536MB GDDR5 2XDVI Mini-HDMI PCI-E DirectX 11 Video Card

• Corsair Vengeance K90 Performance MMO Cherry MX Red Mechanical 20 Key Rollover Gaming Keyboard USB

• [Samsung SyncMaster PX2370] (http://www.samsung.com/us/computer/monitors/LS23WHUKFK/ZA)

• Dell 22inch LCD

• Logitech G500 Gaming mouse

EDIT: Forgot to mention, no overclocking has been done. Kind of worried about breaking something

Lets say I have .. a 1k budget. What would be the most efficient upgrade path?

Thanks!