Personally i would swap out the CPU/MB and go for a haswell CPU and a m/b which has more than 1 PCIe @ 3.0.
Intel Core i5-4670K - Better for gaming £20 more
MSI Z87-G45 Gaming - £26 more. - 3 x PCIe 3.0 instead of Asus H87's 1 x 3.0 and 2 x 2.0 (x4) - this will give you a better crossfire performance if you eventually go this route (its cheaper than buying a new pc lol) i'm led to believe as the cards will run at x8 x8 in the MSI where as x4 x4 in the Asus.
The Sandisk SSD could be swapped for something like a Samsung EVO which will out perform it for £8 difference, however it will be 8GB less in size.
if your not going to overclock the CPU the stock will be fine.if you had any spare budget left after that then i would go for a better GFX card. (as always it comes down to cost my friend!)