i7-4770k processor - $200 at microcenter (top gaming processor in world)
http://www.microcenter.com/product/413248/Core_i7_4770K_35GHz_Socket_LGA_1150_Boxed_Processor
AMD R9 270 - $180 (any where)
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121823
ASRock Motherboard (USB 3.0, 6 gb/s sata, no room for crossfire/sli though) - $50
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157450
Corsair 600watt Bronze certified powersupply - $70 ($50 with $20 rebate)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139048
pick your case peasants $50-70
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007583 4026&IsNodeId=1&name=$50 - $75
Western Digital 7200 RPM 500 GB HD - $60
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136769
8GB 1600 MHZ DDR3 RAM - $80
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231461
$700. Can be around $500-600 if you use lesser known brands, shout out to @
MMSex power supply
top end
what it can play: Battlefield 4 on Ultra with ease
where you can upgrade:
video card ($100-250+ more but thats just future proofing)
motherboard(better memory performance, more PCIE slots)
add a SSD(obvious. maybe not to your 720p peasant minds though)
bow down and kiss the ring, I just built you something three times as powerful as xbox1 and ps4 for $200 more.