If you're buying a CPU and intend on keeping at stock frequencies, go for the 8350.
The difference between 4 GHz and 4.7 stock isn't going to be that big in games. So if it is mostly for gaming, go for the cheaper option : the 8350.
If you intend to buy that CPU not only for games, but also for heavy video/photo editing and rendering, than God Yes, go for the 9590. Yes, you will need a top of the line motherboard and PSU for it (also a really good cooler), but it will be worth it, even compared to an OC'd 4770K.
Also, it is implied that if you choose the 9590, it makes only sense you overclock it, seeing that it has a 220 TDP (it's basically your allowed space to OC)
PS: You said "for the next 1-1.5 years". In the next 1-2 years I think that parallel computing will gain heavy traction within the industry and seeing how the next-gen console already run on 8 core AMD cpus ... guess how's how going to affect your performance in the long run.