Maybe find a cheap E5-1680 v3, and replace the 4gb sticks with 8gb.
might have to check & confirm but you could probably put a high end V4 xeon in there that will give you lots of cores and ram is always that helpful.
Being the old DDR4 components you could probably pick both up for little $$$$ via ebay.
Now both that and the i9 system are massive over kill going by your current load.
Normal wisdom is that the modern consumer chips is the i9 are the way to go because they'll perform better and use less powert (especially if the system load is load or pretty much at idle).
Your i7 system out performs the 1620v3 and uses less power in doing so.
https://www.cpubenchmark.net/compare/2047vs1907/Intel-Xeon-E5-1620-v2-vs-Intel-i7-4770
But what you've got at the moment is as far as that platform goes other than perhaps a faster processor,
So then we look at the return on investment. Find an online power calculator and work out the running cost on the T5810.
Then look at the cost of the new motherboard/CPU/ram (if the Dell is using RDIMMS you can't carry them over the i7 is DDR3) and probably a new case.
Though a new case would give new drive bays - that T5810 seems rather lacking unless there's more hidden away than just the two at the bottom.
Then work out the running cost for a new system.
Then comparing the two work out how long it would take you to recover the costs of the new components based on power savings.
Anything over 2 years, stick the dell and upgrade down the track.