i would get a new motherboard maybe a asus maximus 4/5 i would keep the 2500k and put a good cooler on it and overclock it as much as u can (4.5ghz!) get a new case just so it looks like something new. get a ocz agility 4 ssd 120/240gb no smaller as they fill up quick. maybe a bigger storage drive2/3tb and maybe sell the hd6870 and get a gtx 670
The motherboard that I put in the second list is the one I was planning on getting and the i5 CPU is locked so cannot be over clocked unfortunately! Also the SSD is just for a boot drive that's why I put only a 60GB one as I already have a 1TB normal hard drive (which isn't even half full!) As for the graphics card, that is currently on it's way back to ebuyer.com as it was faulty again! That's the third one I've had! Therefore I might swap the 6870 for an NVIDIA card if ebuyer.com agree that it is faulty, I not then I will have to keep the 6870.
My budget I forgot to mention in my first post is only £180