I do have home plugs and it is one of the routes that I've tried. The problem I found is during a power outage or other issue the power adptor would lose connection with the primary network and require an additional process to get the network back up and all units talking.
All of this wasn't so much of an issue when I listened to the system more and had more time before children but now each time I have power outage it would take 15-20 minutes to get the NAS, Home plugs, SBT back on line to listen to a piece of music (by which time my window of opportunity has passed) it is exactly this reason the SBT has been sat in position for the last 18 months without being powered up again.
In reality I think I know I need to bite the bullit and have a new hardwired connection between primary router and living space put in, it's not a massive house but I suspecty teh sketchy wi-fi is due to having to pass through a couple of external walls where extensions have been put in.
I am making progress but primarily in reminding myself of my grumpy side and reminding myself of the previous issues I found. Cds have been archived in the loft years ago so I have been listening to only 20 CDs over the last 18 months which is now quite painful.