Your builds on the right track, but there are quite a few things I would recommend against:
1). I would replace that G4400 CPU with an Intel i3 6100. You would have a lot less CPU bottlenecks with the i3 6100, and room for CPU upgrades in the future. If I'm not mistaken, that same motherboard would work with the i3 6100.
2). I would upgrade the PSU to an EVGA Super Nova GS 550W, linked here, for added reliability, safety, and performance.: (https://www.amazon.com/dp/B00UVN20UO/ref=twister_B00NAQB7S0?_encoding=UTF8&psc=1). 550W version would be fine.
3). Do NOT buy a GTX 950 for that price. A GTX 1060 will cost almost the exact same and run much, much, much better: (http://www.newegg.com/Product/Product.aspx?Item=N82E16814500402&cm_re=gtx_1060-_-14-500-402-_-ProductO
With the mentioned above upgrades^, you would be able to play the vast, vast majority of games on 1080p settings, with most of them on "high/ultra" and well above 60+ fps. Some very new games will run at ~50 fps.
Here is a link to see what your FPS would be like with these changes: (https://www.youtube.com/watch?v=Zy75qI-m7ew)
Cheers mate, hope this helps.