A pair of 2680v4's certainly didn't decrease your power usage unless you came from Nehalem's.
My 2660v4's in a DL380P G9 idled at 220w. Getting rid of that machine and moving to Alder Lake was the absolute best thing I did for my home server. The new system runs circles around those ancient Xeon's and consumes less than half of the power. I went from averaging 200kwh/mo with the HPE to ~80kwh/mo. $30/mo savings paid for the entire upgrade to a better platform.
Are you intending on running this as a 24/7 machine?
Keep in mind, these are power hungry processors that don't idle down particularly well that have overall performance of a potato.
You had mentioned euro in your post which tells me that you likely pay quite a lot for your electric. These machines are dumpster fodder except for occasional use as a learning machine, definitely not worth running 24/7. Especially when a Intel box from the last 5 years will out perform it on significantly less power.
If the OP is going to use it as a NAS, OP should get rid of it. Westmere is worthless for a 24/7 server. You'll pay more for power in a year of running it than what a new machine with better performance would cost.
I agree that using old R730's for Plex or a home server is silly. Getting rid of my HPE DL380 G9 (the HPE equivalent of a Dell R730) was the best thing I ever did.
For low end budget? i3 12100, Gigabyte Gaming X Z690 DDR4 or Aorus Elite DDR4 motherboard, Unraid, 2x8gb DDR4 3600 (I've been using Corsaor LPX for the last dozen+ Unraid builds I've done). Fractal R5 case with a Thermaltake GX2 PSU.
That should land you just a smidge above $500, not inclusive of the Unraid license.
i5 13500 is an excellent upgrade if you are anticipating running compute heavy tasks. Definitely pick up a pair of 1TB NVME to run as wrote cache and storage for your containers (Plex and whatnot).
Sell the R730's. A single 13500 will likely be more powerful than both of them combined, not that you need the power in the first place. If you get lucky you can find some dolt that will pay a premium for them because they think Xeon's are so powerful and cool!
Profit. Literally. You'll make your money back in not paying to power a R730 (or worse, two of them).
Hard no.
That machine will cost you more in power than what you could have built a modern server for that will decimate that Dell relic in performance.
For $500 you can build a brand new, complete machine based around a i3 12100.
For comparison, a cheap 12100 has three times the compute power of that Xeon dinosaur, plus hardware transcoding. The 12100 will do 6+ 4K transcodes, that Xeon will do zero.
Yes, $50 up front is cheap. It will cost you far more in the long run while having garbage performance.
You've not actually started what your uses are for the machine.
Which vehicle is better, a Duramax 3500 or a Chevy Bolt?
Both excellent vehicles with hugely different use cases.
I've been using Thermaltake GX2's. They're $50 and still maintain a Gold rating. For the marginal difference on an electric bill going from gold to platinum, it would take me 10 years to make up the difference in cost of the PSU.