Should I upgrade my current comp or buy new?

Hi everyone, I just wanted to start off by saying the computers, company, and forum members here all look top notch and I'm excited to possibly buy my first custom gaming rig here. Now for what I need help with.

I'm looking to have a solid computer to last me for about the next 3-4 years with little to no upgrades but will still provide a solid gaming experience and general usage. The games I'm interested in playing at a reasonably high setting, doesn't have to be maxed out, are diablo 3, FF14, SC2, WOW, SWTOR, Call of Duty, etc.

My current comp is a lame storebought Gateway model with a amd x2 duo core processor @ 2.8mhz with 2 gigs of ram and a geforce 7900 gs. Is it worth upgrading any part of this to achieve what I'm looking for above?

For the comp I'm looking at, I have a budget of $1,500-$1,700 and this is the setup I've come up with.

Chassis Model: Special Deal Hot Seller - Cooler Master CM Storm Scout
Processor: Intel Core i7 860 2.80GHz (Quad Core)
Motherboard: EVGA P55M SLI (Intel P55 Chipset)
System Memory: 4GB DDR3 1600MHz Digital Storm Certified Performance Series (Highly Recommended) (Hand Tested)
Power Supply: 750W Digital Storm Certified (Dual SLI Compatible) (Silent Edition Recommended)
Hard Drive Set 1: Operating System: 1x (500GB Western Digital (16MB Cache) (7200 RPM)
Optical Drive 1: DVD-R/RW/CD-R/RW (DVD Writer 24x / CD-Writer 48x)
Optical Drive 2: - No Thanks
Internet Access: High Speed Network Port (Supports High-Speed Cable / DSL / Network Connections)
Video Card: 1x NVIDIA GeForce GTX 460 1GB (Includes PhysX Technology)
Sound Card: Integrated Motherboard Audio
Extreme Cooling: AIR: Stage 1:Coolermaster V6 Single 120mm Fan Performance Cooler (Compatible With AMD, i5, i7)
Chassis Airflow: Standard Factory Chassis Fans
Boost Processor: FREE: Stage 1: Overclock the processor between 3.3GHz to 3.9GHz (Cooling Upgrade Recommended)
Boost Video Card: - No Thanks, Please do not overclock my video card(s)
Boost Memory: - No Thanks, Please do not overclock my memory
Boost OS: - No Thanks, Please do not tweak the services on the operating system
Windows OS: Microsoft Windows 7 Home Premium (64-Bit Edition)
Restore Kit: Digital Storm Specialized Recovery System (DVD Image Based)
Virus Protection: - No Thanks
Office: - No Thanks
Benchmarking: - No Thanks
External Storage: - No Thanks

Cost Before Shipping with 10% discount: $1,453.00

Please let me know if there are any parts: mobo, cpu, gpu, etc that you would upgrade/change. Also, I see that a lot of people choose the x58 i7 over the p55 i7 but I don't know how much I would benefit from it considering my computer usage.
Thanks you for any input.

Yes i think with a budget like 1700 i can help you get a build with an x58 mobo. as for your question, a higher cache helps load things faster and with multitasking a bit too. Higher is better is all you gotta know but i suggest the 32mb over the 64 because there is a very small performance increase and wouldnt suggest it to someone with a budget.

Here is a build you might consider, you can change a few things if you want a better hard drive + ssd but if you can get your budget up to 1850 you can add a 40g intel ssd in tehre for OS/apps and a 500g for storage.

Ticket Number: 426077
Total Price with Instant Savings: $1,700.00
Direct Load URL: http://www.digitalstormonline.com/comploadsaved.asp?id=426077
Specifications:
Chassis Model: Special Deal Hot Seller - HAF 922
Processor: Intel Core i7 930 2.8GHz (Quad Core)
Motherboard:  EVGA X58 Micro Edition SLI (Intel X58 Chipset)
System Memory: 6GB DDR3 1600MHz Digital Storm Certified Performance Series  (Highly Recommended) (Hand Tested)
Power Supply: 750W Corsair TX (Dual SLI Compatible)
Expansion Bay: - No Thanks
Hard Drive Set 1: Operating System: 1x (500GB Western Digital (16MB Cache) (7200 RPM)
Optical Drive 1: DVD-R/RW/CD-R/RW (DVD Writer 24x / CD-Writer 48x)
Optical Drive 2: - No Thanks
Internet Access: High Speed Network Port (Supports High-Speed Cable / DSL / Network Connections)
Video Card: 1x NVIDIA GeForce GTX 470 1.2GB (Includes PhysX Technology)
Add-on Card: - No Thanks
Sound Card: Integrated Motherboard Audio
Extreme Cooling: AIR: Stage 1: Noctua Dual 120mm Fans High Performance Cooler (Compatible With ONLY i7 Processors)
Chassis Airflow: Standard Factory Chassis Fans
Internal Lighting: Internal Chassis Lighting System (Blue)
Boost Processor: FREE: Stage 1: Overclock the processor between 3.3GHz to 3.9GHz (Cooling Upgrade Recommended)
Boost Video Card: - No Thanks, Please do not overclock my video card(s)
Boost Memory: Memory Fan Kit Only (Does not include memory overclocking service)
Boost OS: - No Thanks, Please do not tweak the services on the operating system
Windows OS: Microsoft Windows 7 Home Premium (64-Bit Edition)
Restore Kit: Digital Storm Specialized Recovery System (DVD Image Based)
External Storage: - No Thanks
Exclusive T-Shirt: - No Thanks
Priority Build: - No Thanks, Ship Within 5-15 Business Days After Order Is Successfully Processed
Warranty: Life-time Expert Customer Care with 3 Year Limited Warranty