Very few games do. Most games use 2 cores at most, and Intel has way ahead IPC than AMD does.
This is probably your best upgrade for the time being, if you plan on upgrading the graphics card when it starts delivering less-than-wanted performance. (recommended)
PCPartPicker part list /
Price breakdown by merchant /
Benchmarks
CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor (£184.24 @ CCL Computers)
CPU Cooler: NZXT HAVIK 120 75.8 CFM CPU Cooler (£37.90 @ Scan.co.uk)
Motherboard: MSI Z87-G43 ATX LGA1150 Motherboard (£91.32 @ Aria PC)
Total: £313.46
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-08 23:17 BST+0100)
This, instead, is probably your best bet if you plan to stick with whatever you get now until you completely change your PC over.
PCPartPicker part list /
Price breakdown by merchant /
Benchmarks
CPU: Intel Core i3-3220 3.3GHz Dual-Core Processor (£88.79 @ Aria PC)
Motherboard: ASRock H77 Pro4/MVP ATX LGA1155 Motherboard (£66.55 @ Ebuyer)
Video Card: MSI GeForce GTX 660 2GB Video Card (£147.96 @ Dabs)
Total: £303.30
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-08 23:19 BST+0100)
Bad quality PSU usually have a few problems:
- they degrade fast in time, which means someday your system will simply not boot
- they don't provide high amp on the +12V rail, which means they can't even start up middle-to-high end GPUs
Remember that a PSU blowing up can easily damage other components of your computer, you don't want to cheap out on it.