A wireless router used as an "adapter" would be a wireless bridge. Not all WIFI routers support that functionality. Asus routers all support that functionality. You can get a RT-N56 used on E-Bay for about $20.
The benefit of using a router as a wireless bridge is that you can move it to get the best signal. Then you run an ethernet cable to your computer. A WIFI adapter is stuck withing a few feet of your computer (or directly attached).