there is no TL-WR2843ND
TP link will have something more exciting at the end of the year.
id say linksys because its the daddy but asus is good too with tomato firmware and yes because your house is 4 floors tall putting a router in the middle is a wise move.
you could set up a access point/power line adapters.
if youve got money to test then go for it and return whatever you dont need, wont work. double check thr stated rights but by law youve got a right to a refund.
mode 54/145/300... SuperHub? no. modem mode linked to your own choice of router