to upgrade the stone age pc

[Tan_hong_sheng]

will an i5 2400 bottleneck a 1070 or 1080

 

[BurgerandChips66]

On some cpu intensive titles I would say yes, it will.

 

[hang-the-9]

Depending on the card you have now, it may be worth the upgrade, and if you are planning to upgrade the rest of the system then the new cards won't be a waste. Although you can go a rung lower than the 1070 and still be OK with that CPU. I'd probably max out at the 950 or R9 370 or 380 with that CPU to keep things balanced.