desktop upgrade to workstation - advice needed

[madLyfe]

ive been using this i5 haswell with 16gb ram since 2013 and im looking for advice on what kind of older and used hardware i can cheaply cobble together as a replacement. my current setup and use is running 3 monitors off my RX470 GPU, heavy browser use with tons of tabs/youtube/PWAs, dev environment, and VMs. i do very little to no gaming. i mainly run KDE Neon but have a dual boot setup with win10 for fusion 360.

i guess my requirements would be something with at least 64gb of ram and something that can perform equally or better than than the i5 haswell. i dont really care if its a server mobo based but i already have dual opteron boards that i wouldnt touch because they have crazy idle wattage. id say DDR3 and PCI-E 3.0 would be a base as well.

i see so many version of SM boards and Intel CPUs that im not really sure where to start.

 

[madLyfe]

trying to keep things as inexpensive as possible, would it be a bad idea to go with an HP Z440 workstation board(specs)? would probably put 2 or 4 DDR4-2133P PC4-17000 16GB sticks in it. not sure about the CPU. im just looking to see if i can get a system better than my i5-4670 CPU @ 3.40GHz with 16gb of ram. my use is heavy browsing/videos and dev stuffs with vscode and some compiling. i do run VMs and would like to not have to dual boot win10 but run it reliably in a VM from my linux desktop.

things that i think are important are USB 3, PCI-e 3, and a lot more ram than i currently have. im trying to keep the build below $300.