I think the 850 psu is overkill but i also wouldn't recommend buying it because isn't a certified power supply so it hasn't got an 80+ efficiency rating. I would advise maybe a 600-650w 80+ bronze power supply.
Also your motherboard is a Z87 so it supports overclocking yet your cpu is the 4770 so it doesn't support overclocking so i would advise paying a bit more for the 4770k and overclock or if you aren't going to overclock then i would look for a different motherboard because i would presume that the Z87 boards are more expensive.
You might want to buy a cpu cooler instead of using the stock cooler, unless you have one listed but i couldn't see it. I have the 3770k and its great and the 4770 is an upgrade so it should be good. The only real way of future proofing it more is to get a better graphics card but the term future proof depends on the persons demands from their computer. If you are ok with medium graphics then you should be fine, if you want high or max then i would advise changing the gpu.