zqa20 :
He want's a pure gaming machine. Don't really want to deal in second hand parts.
In that case I'd best let someone else makes some suggestions as my speciality
is getting the maximum value from 2nd-hand parts (though having said that, many
of the things I buy are actually new, just sold off as normal auctions); even today
it's hard to beat a 2500K, Z68 board and a couple of decent former high-end GPUs.
(the rig I built is quicker than a GTX 780).
Note that if you don't intend to do any overclocking, then you'll get better performance
from a non-K i3 or i5 matched with a suitable GPU that stays within budget. toms has
just updated their best-GPU article.
Ian.
PS. Quick extra thought - do you already have any of the items required for a complete
system? ie. case, PSU, etc.? Or is it entirely to be done from scratch?