Effectively it is slightly slower than an i3 8100 or Ryzen 3 2200G. The platform is more robust though, The LGA 2011 socket will fit 6 core CPUs and quad channel RAM. The problem is that something like a Ryzen 5 2600 is about equal to the fastest CPU that you can fit to the platform... the only advantage to the platform is the memory bandwidth. In quad channel with its DDR3 it is still faster than DDR4 dual channel. For gaming memory bandwidth won't really matter though. LGA 2011 system are more usually workstation systems.
Given the age and capabilities, I'd sell it around the price of a comparable low end gaming machine. No advantage the platform has really applies to average use.