Upgrade the motherboard. The i5-3570k is being held back by that h61 board. Get a decent z77 and let it loose.
SSD. Some will argue that an SSD is no help in games, but I have found this to be untrue. In many games that have repetitive loads (same cell, same actor, same map etc) after the initial load is cached to the SSD temp files, they load from the SSD, not from Hdd, making uploads much faster. 30 seconds to load a 4k texture map, or 5 seconds, its your game time.
HDD. That 500 is more than likely getting close to full working ability, or about 450-460Mb tops. Any large games, further added to with upgrades, mods, texture packs etc, are really gonna eat away at that space, 500 is not that much, considering Windows fresh install will eat 35-45 by itself. A move upto a seagate/wd/Toshiba 1Tb wouldn't be a bad idea, especially considering the performance you get for the $50 price tag.
Gpu is fine, for 1080p it'll do the job, albeit not at the highest detail settings in some games.
Psu. Cheers, its an excellent unit, and it'll handle the most powerful single gpu made, the gtx980. So hold onto it.
Ram. Your choice, but most games won't come close to filling out 8Gb, more like 5-6, so size is good. Intel cpu's are certified for 1333/1600MHz. Anything higher and you start to loose that nice 1:1 ratio which really starts to work the memory controller. This results in elevated temps on the cpu. Also, more than a few 2133 MHz and everything 2400MHz and up require 1.65v, not the normal 1.5v, and this is not good for Haswell or later cpus as the VRM's are on die, not separate as in sandy/Ivy Bridge. Difference in 1333 and 1600 is a few frames, like 1-3, you'd never notice the difference.