For wifi... only option would be put your rig and the main router closer together.
I'm not a great techie when it comes to network management. I'm the plug and play guy... that's why I love Apple!
If that Coax is your internet... or just cable?... run an ethernet through that hole too, and go straight to the main router...? If that's even an option. *shrugs
Sorry I can't offer a better solution. I just know when I started having problems streaming to my AVR, everybody said exactly the same thing... not to use an extender, and if I have to use wireless, do the 2.4 network, not the 5ghz network.
Cheers Buddy!