upgrade x51 r2 or rebuild completely?

so i need new graphix as the 645 aint gonna work for games comming out after summer, my hdd crashed a month after the one year warranty was up, the memory always played up and i need new ones of that..

and when i decided to updgrade i get to know i cant do as i want as i only got 240 psu... 

so the choice is, go for okeyish grapfix new hdd and ram,

or buy new chassi, graphix, memory, ssd hdd, motherboard and cpu fan.. i want to keep the cpu atleast as its a really nice one... 

my budget is around £250 and im not sure a new computer is possible on that price? 

if so what can i do with the current parts i got and is it even possible to keep the cpu and put it in an other motherboard?