"When a WIRELESS router says 300mpbs, you won't get anywhere near 30MB/sec."
Completely and utterly agree with you!! Then they shouldn't report it as such! Just like when they say 54mbit for G, at best you get about 23mbit or about 3MBps
Its pure marketing nonsense how they report wireless RAW total bandwidth, while in wireless there is a **** load of overhead! So if you head over to smallnetbuilders wireless benchmarks N at 40mhz your looking at like 60mbps tops which ok your 100mbit wire can handle.
My point is they are putting 300Mbps on the box -- when clearly that can not be the case if the wire connections are only 100

Who are they thinking they are fooling?
Also to the OP, unless your going to be connecting something else to the gig switch that can do gig, there is NO point to getting it for your nas if then connecting that to a 100mbit switch on your router and your using wireless anyway.
I would wait to get the switch until you have have other devices connecting at gig. Or you move to a wireless speed that is over 100mbit, ac is out there for example. Some of the 3 stream N can get over 100. But then your going to need another wireless router.. Which will prob have gig lan ports.
To be a bit clearer Detections drawing should of shown a gig connected pc and a 100mbit connected pc vs just the one with both connected and wireless client.
Think of it as a road connecting the devices - if at any point there is a lower speedlimit, then that is the fastest you can go on that path even if part of the path is faster. Example you have a 10/1 mbit internet connection 10 down and 1 up.. Does not matter if your computer was connected to router at 10Gb fastest your going to download is 10mbit