Ethernet cables and terminations are known as a "transmission line". If they aren't terminated in the characteristic impedance of the cables, a portion of the signals reflect back to the input. So, one device is better able to handle these reflections from the hanging cable.
Any switch and especially ones with an auto-MDIX port make it easy to expand the capability of a jack. Some early switches had UPLINK ports which reversed the transmit and receive pairs. auto-MDIX is required for Gigabit Ethernet.
Your best bet is to wire a patch panel for the premise wiring and to upgrade to a switch like Nigel suggested. Allocate internal (LAN) stuff to the switch and the high bandwidth WAN stuff to the router ports.
If you want cheap, then a 5 port switch which gives you 4 extra ports for every one. You don't buy a router with more ports. The earliest router I had had one LAN and one WAN port, because that;'s the function of a router and that;s what it needs. They are now combo-boxes and contain firewalls, switches, routers etc,