I just stumbled onto a Dell Xeon 5670 T7500 for around 50.00 USD. Is there any way to beef up this system? I already put a GTX 1660 ti in it.
Honestly that is still do this day a pretty beefy little workbench besides a GPU (which you have already done) there is not much you can do realistically. You already have the top of the line CPU for that socket and a ton of ram maybe just add an ssd?
There are 6 core X5680, X5690, and 4 core X5687 cpus that are faster. The memory controller is on the CPU so 1333 will be your RAM speed. Be sure and stay with 3 channel RAM setups. You could add a 2nd CPU if you want to.