Plug in your preferred 3CX supported phone. That headset should work with just about any phone but you'd need to use to guide or call Plantronics to make sure you have the appropriate cable/EHS adapter.
I use a $20 refurbished Turtle Beach gaming headset at home with the 3CX softphone but it's just a straight audio device, no call pickup via buttons or anything like that. Not the most professional look either. But the soft phone will work with any audio device. If you want specific business ones most vendors compatibility guides like the Plantronics one I listed have 3CX Softphone as a selection to find compatible headsets. I have a Jabro Pro at the office but it's not cheap.
