The other solution you could consider is expensive and assumes that the house electrical system was put together properly.
With powerline 500 series your could have as many as 4 wireless systems installed to provide proper coverage.
The powerline kit I recommendOne powerline would go in the room with the existing cable modem and router being used then you would place another powerline in the other room and attach an Access Point to it and in that way you cold get coverage where you need it. You would need to properly configure the router and access point(s). Do some research on powerline stuff.
Or You could try the R6300 in the current location [where your modem is situated] and see how well it performs in your environment. It may surprise you and me
with powerline added you then could then very easily extend your network by adding another R6300 in
client mode and really have a dynamic system in place
With POWERLINE networing you cannot use power strips -- you must have direct acces to the electrical outlet in each room of interest. If this house is in an area that is subject to a lot of electrical storms then I would discourage the use of powerline networking.