Do I use an old Comp for a NAS? Or newer existing?

[Enquiries]

Do I use a newer
B550M-C with Ryzen 7 3700x 8-core 16 threads (65w)
OR an older
P8Z68-V with Core i5 2500k 4-core 4 threads (95w)(sandy bridge 2011)?

Info:
Currently have both at home. And instead of buying a new NAS, I would like to buy a newer AM5 socket Motherboard/CPU combo that is on sale at my local micro center to upgrade my work (CAD and GAMING) rig and use the slightly used or older hardware for the NAS.

The Sandy Bridge is used by my daughter for gaming and homework with no complaints.
And since it seems to be the less efficient of the two systems, would like to leave that one alone since its not on 24/7
And use the newer 8 core 65w for the NAS since it will be on 24/7. I currently pay .30/kwh.

I will be sourcing additional parts on the used market but can extend the budget further If its used to for my AM5 rig.

I would like to be able to stream movies and maybe host my website locally in the near future to reduce hosting cost.

your time is really appreciated

[ed]

It is recommended to use the Ryzen 7 3700x with B550M-C motherboard for your work (CAD and gaming) rig as it has more cores and threads which will result in better performance. The Core i5 2500k and P8Z68-V motherboard can be used for your NAS setup as it will be on 24/7 and the Ryzen 7 3700x will consume more power and lead to higher electricity bills. Also, the Ryzen 7 3700x is a newer and more efficient setup for streaming movies and hosting a website locally, but make sure to check if the B550M-C motherboard supports the necessary components for these tasks.