Is Upgrading to an RTX 5070 Worth It for My 10-Year-Old PC?

I suggest looking for a used Intel 9700 or 9900 on the second-hand market to pair with your system. The 6700k and RTX 5070 together isn't the optimal combination.

Depending on your gaming resolution, the 6700k might still perform okay at 1440p or even 4k, but its performance might be limited. It really depends on the games you plan on playing.

For a more balanced setup, consider the RTX 9070. It tends to have less driver overhead, which could help improve your performance overall.

You shouldn't experience a significant bottleneck with the RTX 5070 in your PCIe 3.0 setup. You will definitely notice the difference after the upgrade. However, if you really want to maximize performance, consider upgrading your CPU too. I did a similar upgrade from a first-gen Ryzen to a 5600x with a 4070 Super, and the improvement was fantastic.