This would be a huge upgrade for you.
PCPartPicker part list:
http://uk.pcpartpicker.com/p/2YMoX
Price breakdown by merchant: http://uk.pcpartpicker.com/p/2YMoX/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/2YMoX/benchmarks/
CPU: AMD Athlon X4 760K 3.8GHz Quad-Core Processor (£57.78 @ CCL Computers)
Video Card: Gigabyte GeForce GTX 750 1GB Video Card (£89.59 @ Amazon UK)
Total: £147.37
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-04-24 16:40 BST+0100)
But I recommend spending £17 more and getting the GTX750ti if you can.
PCPartPicker part list:
http://uk.pcpartpicker.com/p/2WEzW
Price breakdown by merchant: http://uk.pcpartpicker.com/p/2WEzW/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/2WEzW/benchmarks/
CPU: AMD Athlon X4 760K 3.8GHz Quad-Core Processor (£57.78 @ CCL Computers)
Video Card: MSI GeForce GTX 750 Ti 2GB Video Card (£106.99 @ Amazon UK)
Total: £164.77
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-04-24 16:42 BST+0100)
You could sell your A6 and 7750 and get some of your money back, and then maybe add another 4GB of RAM or get more storage if you need.