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.
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).