Is my "gaming setup" okay?

[moosa32365]

I have a Dell Optiplex 755 dual core at 2.66 ghz. 2 pci conventional, 1 pci-e x 1, and 1 pci-e 2.0 x16, 4 GB RAM, i'm using 4GB VRAM, and im using win 8 pro 64 bit. I am currently using an MSI Nvidia GT 520 Fermi, and i'm going to buy either an EVGA gtx 650 ti, or super-clocked but i also don't know which is better. If I were to get it would it let me play games like skyrim, crysis, and AC3 on MAX settings at a steady 60 fps at a 1600x900 resolution?

I just need to know if ill be able to play or not, and if possible, i need to find out which cpu to get for my dell motherboard.
I have the full tower dell optiplez 755 and when i bought it the salesman said it was socket LGA155 but it's not -_-.
I'm also using the stock Power supply which i think is 350 Watts.. do i really HAVE to upgrade it to 400-450 for my new GPU?

Heres my PC manual:
http://www.dell.com/downloads/global/products/optix/en/opti_755_techspecs.pdf

And the GPU's:
GTX 650 Ti
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130838

GTX 650 Superclocked
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130828

I'm also thinking about upgrading to the max 8GB RAM with 4GB VRAM

 

[angaddev]

so what are you upgrading? Mobo and cpu or just gpu?
yes, you should buy a new psu, for peace of mind, because you don't know how reliable the one inside the computer is.
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i3-3220 3.3GHz Dual-Core Processor ($109.99 @ NCIX US)
Motherboard: MSI Z77A-G41 ATX LGA1155 Motherboard ($83.99 @ Newegg)
Video Card: Sapphire Radeon HD 7850 1GB Video Card ($164.99 @ Newegg)
Power Supply: Corsair Builder 500W 80 PLUS Bronze Certified ATX12V Power Supply ($39.99 @ Newegg)
Total: $398.96
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2012-12-31 04:34 EST-0500)

 

[angaddev]

Just a note, the 650Ti will not max out your games even at 1600x900. The 7850 will manage, though maybe around 50fps rather than 60

 

[moosa32365]

So this mobo will fit inside my case?

 

[raja10]

buying nvidia 660 ti or 660 or 650 ti is best or going for radeon 7870 ghz or 7770 is best

 

[angaddev]

7870 is best. No need for the ghz edition, buy the cheapest card you can get and overclock.