take a look at www.ncix.com
click on custom computers
ncix is a huge retail seller of computer parts and they build computers as well. i was playing around and the prices seem pretty reasonable.
for a general gaming computer i would say:
assuming you want to overclock
i5-4670k
at least a hyper 212 evo cooler if not better.
z87 motherboard from asus
8gb 2x4 1600mhz (or 1866mhz if not much more) ram from corsair, gskill, mushkin
120 or 240gb ssd for boot (would suggest samsung or intel)
1tb hdd
650w psu (or 750-850w if you want to add a card in later on) from seasonic or xfx. (can use a corsair RM or HX though as well)
780ti graphics card
corsair 750d case
something along those lines will max bf4 at ultra at 1080p. might need to sli to do 1440p at ultra or drop down to high. see this link for estimated performance.
http://www.bit-tech.net/hardware/graphics/2013/11/27/battlefield-4-performance-analysis/3
i used an i5 since you really dont need an i7 for gaming (it adds hyperthreading) though if you intend to do not just gaming but other tasks or if you want to record games then you could step up to an i7.
if you dont want to overclock then get a non K suffixed cpu (like the i5-4670) with a h87 motherboard instead.