Thinking of building my own lab server for core development work. 16GB RAM/Core i7 processor on my mind....What specs work for you?

That seems like a pretty nice machine for even a pretty medium-high end web server. Is it mainly for web dev/db work? Not for power, but it can also be fun to cluster a few Raspberry Pi's if you're looking to test a distributed/HA system.

i have 7 Pis, thinking of doing something like that...

The PI's can also be leveraged during a disruptive event when you might not have access to your primary laptop ie fire evacuation.