Your CPU isn't so weak but if u wanna go a FX-6300/6350 is good.
And another exactly same 4GB memory to pair.
Your HDD is slow so get a new 7200rpm HDD or get a SSD instead.
Your gfx is obsolete now. If u wanna keep your PSU, HD 7790 and GTX 650 ti boost is the best shot;
If u wanna upgrade your PSU and gfx:
PCPartPicker part list:
http://pcpartpicker.com/p/1mJFi
Price breakdown by merchant: http://pcpartpicker.com/p/1mJFi/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1mJFi/benchmarks/
Video Card: XFX Radeon HD 7850 1GB Video Card ($138.98 @ Newegg)
Power Supply: Corsair CX 600W 80 PLUS Bronze Certified ATX12V Power Supply ($57.99 @ Microcenter)
Total: $196.97
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-05 12:44 EDT-0400)
or
PCPartPicker part list:
http://pcpartpicker.com/p/1ovkO
Price breakdown by merchant: http://pcpartpicker.com/p/1ovkO/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1ovkO/benchmarks/
Video Card: HIS Radeon HD 7870 2GB Video Card ($179.99 @ Amazon)
Power Supply: Corsair CX 600W 80 PLUS Bronze Certified ATX12V Power Supply ($57.99 @ Microcenter)
Total: $237.98
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-05 12:46 EDT-0400)
In the full upgrade bundle:
PCPartPicker part list:
http://pcpartpicker.com/p/1ovn2
Price breakdown by merchant: http://pcpartpicker.com/p/1ovn2/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1ovn2/benchmarks/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($109.99 @ Amazon)
Storage: Sandisk Ultra Plus 128GB 2.5" Solid State Disk ($87.99 @ NCIX US)
Video Card: HIS Radeon HD 7870 2GB Video Card ($179.99 @ Amazon)
Power Supply: Corsair CX 600W 80 PLUS Bronze Certified ATX12V Power Supply ($57.99 @ Microcenter)
Total: $435.96
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-05 12:48 EDT-0400)
Just for reference, what's your thought?