I would go with an i5 2500k i dont think the i3 is a very good gaming cpu and then you can use the same mobo. ive never heard of that psu brand but im new to this. Unless you plan on getting another 6870 down the line a good 500W psu will work fine. These are just suggestions depends on your budget etc...
also, unless your going to upgrade this to an sli rig or have 4-5 hdd while OCing your rig, you dont need a 750w psu, 500-600 should be more than enough - also try to get a named brand, you dont want to brick everything else due to 1 cheap component - to clarify, a cheap psu is generally 2/3 the weight, and that extra weight is gubbins regulating the supply.
rest of the stuff is fine - tho if you can stretch to a 2500k do so
I am finally going to get an i5-2500k and a shappire 7850 dual-x 2gb and I got a question, if the Mob i'm going to get has a pcie3.0, am i going to be able to use it in 2.0 mode (since 3.0 only suports ivb)?o,r it won't work at all? and, is the Asrock z77 pro4 a good choice ?