Yes you can, any of them will work, but you have to use your computer to set them up, then attach them to the HR box.
DirecTV suggests the Linksys (Cisco) WGA600N and has the drivers installed on the HR firmware. You can read all about it here:
DIRECTV: Support : Services : On Demand
Now, if you are hoping to use these for MRV, you may be disappointed. They work great for DOD, but MRV is less than perfect. You are better off with a wired solution, maybe powerline adapters, or waiting for Deca.
Those are not USB adapters, but have an ethernet connection to the DVR. Both the Linksys WGA600N and WET610N can be set up on the HR2x using the setup menu. Other models of wireless ethernet adapters can be used but will need to be setup using a computer unless both the adapter and router support wi-fi protected setup (WPS).
In many cases, the MRV experience with wireless or powerline will be disappointing.