Originally Posted by
Irien
Raven's Nest - it is generally a bad plan to keep buying "incremental" updates - saving for a 1080 when you have a 1070 will result in spending a lot of money for barely 20% speed increase. That isn't going to be noticeable, esp if playing at 1080p etc. Going from a 280 to 1070 was probably a reasonable upgrade, and more significant than 1070-1080.
Your son would be far better advised to wait for future generations, where 1080 prefermance will be available for 1060/1070 prices. For example, I believe the current 1060 generally outperforms the older 980 for much less money.
If you could find a buyer for the 1070 at sensible price, that's about the only scenario where a 1070->1080 would make sense. In other words, if your son only had to pay a further <100ukp on top of second hand price of 1070, then he might feel OK with it. Otherwise, he's likely going to feel robbed.
You also don't say what PC he's putting it in. If it is a fairly poor CPU/RAM or no SSD, then putting an expensive graphics card in the system isn't a magic bullet. For example, I wouldn't suggest putting a 1070/1080 in anything less than a fairly recent i5 (or Ryzen) with 8Gb RAM minimum. You could arguably feed it with a skylake+ i3, but you probably wouldn't be getting the best out of it (certainly for AMD GPUs).
Bottom line - high end GPUs are something of a "mugs game" in terms of value for money. I tend to bite the bullet every couple of years, but there's always something new on the horizon. The 1080ti is looming large, and then in six month's there's be an 1100-series (or whatever) to replace that.
The best advice I can give is to use what you have for as long as you can bare it, then make a big jump to the best you can possibly afford. This will give the biggest jump in experience, and probably the longest lifespan of your current card (ie. value for money).