If you're going to overclock then the choice is easy:
Core i5-4670K - £190
and then get the best LGA1150/Z87 chipset motherboard you can afford with whatever is remaining.
The only Xeon's which are good value for money are the 8 threaded ones, that's because the equivalent desktop i7's are usually over £250.
A Haswell i5-4670K overclocked is probably the best value for money chip you can buy.
Core i5-4670K - £190
and then get the best LGA1150/Z87 chipset motherboard you can afford with whatever is remaining.
The only Xeon's which are good value for money are the 8 threaded ones, that's because the equivalent desktop i7's are usually over £250.
A Haswell i5-4670K overclocked is probably the best value for money chip you can buy.

