Are you set on HPNA? I use 3 of these HomePlug adapters throughout the house where there is no or spotty wireless coverage, and get good results, including streaming of Netflix, Hulu Plus, Amazon video, etc through two Tivos. MRV also works well through them between the two Tivos.
$49 for a set of two, which will get you one Ethernet jack in a remote location.. Another $49 gets you two additional (one goes to the router). They have them at Best Buy