If you still have your old router or the modem does NAT, I'd recommend just adding a dumb switch. Plug it in to the LAN port on the router and it's done.
4/5-port GigE switches are around 50, 8-port around 80.
Manufacturer doesn't really matter as they are simple electronics.
If you don't then I recommend staying away from *Link.
Linksys, netgear and zyxel have served me well (annoying, but working firmwares - unlike d-link's which crashes once an hour)