Hi,
Your post is confusing because:
1) You don't specify what CPU and GPU you have
2) the i5-4690K is not the same socket as the XEON's you listed so what motherboard do you have?
3) How much are those used XEON's you are looking at?
For GAMING, what's most important is:
a) four cores (more rarely helps much), and
b) highest processing per core
In fact, an 8-core Xeon with 3.2GHz Turbo is going to lose in many games to a $110 i3-6100, dual-core CPU.
4) When you say "upgrading" do mean to just change the CPU, or are you talking about building a new computer?
a) if just changing the CPU it has to be listed for your motherboard (see CPU support list at motherboard site), and
b) if building a new system I recommend a SKYLAKE build and probably an i7-6700K since you edit video
You also want 16GB at least for video editing. More than 16GB may or may not help depending on the video, program etc, and of course you'll need SSD's etc for the optimal setup