14Mbps is fine depending on what you're using it for. There have been indications that the STB would use anything from half a meg upwards on what little information we have from them so that is fine. There are
faster versions but they get signficantly more expensive.
Provided you just connect a port on the router to the Homeplug then and the other Homeplug to the STB it shouldn't affect anything else you're doing. Assuming you buy a wireless router then you can use the laptop wirelessly on it. If it's not a wireless laptop/router then standard RJ45 cabling will do the job.