How technology inclined are you? Build a PFsense/Opensense router from an old pc with two network adapters then get Unifi access points. They have been the best wifi experience in my whole life. This route is very technical but will give you the best coverage but will learn a lot. Also running cat6 drops or using power line adapters would be one of the best ways to get the connection around the house. But I have experienced with gfci breakers they can cause problems with them working.
Damn son you got dem AGP graphics! At least that is 1 thing that can be upgraded.