You can just daisy-chain a bunch of these together to get however many ports you need:
NCIX.com - Buy Trendnet TEG-S80G GREENnet 10/100/1000 8 Port Gigabit Switch RoHS - TRENDnet - TEG-S80G - in Canada
Cheap and works fine. Assuming your router has 4 LAN ports, you could hook up 1 switch to each port netting you 24 ports total. Nothing stops you from plugging a switch into a switch either though, so you can have as many ports as you need.
Granted it's going to be sharing bandwidth, but it's unlikely that you'll saturate a Gigabit link that often. Internet access surely won't. Only if you have a ton of LAN traffic it might become an issue.
And if you need to plug 2 devices into a single jack, you could use one of these on
BOTH ends:
For only $2.02 each when QTY 50+ purchased - T Adapter Cat5e 1M/2F - 6 inch | T Adapters
Only downside is that you'll be limited to 100Mbps due to the way it "shares" the single cable.
Placing a single wireless router on the 2nd floor, in the middle of the house, should get you whole home coverage (depends on how big the house is though and if there's a lot of metal in the walls/floor). I'd recommend the WNDR3700 personally as that's what I use. My WNDR3700 resides in the basement, about center in the house, and it covers my whole house, but it's only a 2 bdr bungalow at ~800 sq ft.
Although the ASUS RT-N16 is a good router, it's wireless is lacking IMO. Single band, and just poor signal strength. I still use it though as my router-only, running Tomato firmware. My WNDR3700 is the access point, with stock firmware.