I don't have any spare ports on the router (printers, PC, etc), and I already have a 'full' 4-port splitter (xbox, digital tv, blue ray player, and sonos system). The sonos bridge has 2 ethernet ports. Maybe I can plug a NAS directly into it... that's what I wanted the drive for anyway. But I also want the rest of the network to access it as well. Not sure if this will work.
Just daisy-chain another ethernet switch into the system. Cheap 5-port models are only $20-30. Although for the number of devices you apparently have plugged into the system, you might want to spend the money for a proper 16-port switch
and then use the router as a gateway device only. The overall network performance will probably be better, and the router will live longer since it won't be producing as much heat.