Alright so
CPU switch to 7600k
yep
PSU I swap to Power Corsair CX 650M
that sucks aswell, at least get one with multirails, so corsair vengeance 550 for example. that is at least solid. or get a SuperFlower HX 55, that would be even better. the important bit is that a good psu might save you a lot of trouble, especially when OCing
Fan I switch to CPU Deepcool Gammaxx 400 + Fan case CM Color 12cm
for the cpu cooler go for something larger, something in the area of 50 bucks. still saves you a lot compared to AiO water, but is suited for OCing
So any tips for choosing a decent GPU that can still be used in around 5 years?
no gpu will last that long, but if you can get it a 1070 would surely be enough for quite a while. if you can get one, the palit or gainward customs are the best 1070s
on which website are you planning to buy? i would be able to suggest specific products then, would make it a lot easier