[Nexus Player Q&A, Help & Troubleshooting] innoman:
I think there is a little bit of confusion. My Plex Server/PC are on say port 1 of my 16 port gigabit switch and is communicating with the switch at ~1Gbps. My NAS is on ports 2/3 and both ports are at a Gigabit (each NAS port has it's own IP--one is just used for my Mac and phone backups, the other is predominately used by my PC for Plex shares and whatever other files I put on there) and my FireTV is on port 4 at 100Mbps (limited by the FireTV). (I do not connect a hard drive to my Fire TV, I think someone else said that). I can stream to 3 different TVs (using a mix of a google TV (wired), Chromecast (wifi) and Fire TV (wired or wifi--same results either way) without any issues, buffering or otherwise, at full 1080p with ~12GB files all using Plex. It works near flawlessly most of the time. The only issue is that the Fire TV doesn't stream 5.1 audio (most of my content is AC3) UNLESS I use an external player (XBMC, etc...)--lots of info about this in the Plex forums.

The Fire TV does not have 802.11ac, it has 802.11n. Having it connected to an 802.11ac access point doesn't offer any real benefit other than they tend to do 802.11n slightly better than most 802.11n routers, presumably because they tend to be more powerful. There is no benefit for putting my FireTV on wifi over Ethernet--none what-so-ever since there is already an Ethernet port right next to it--because it will only add traffic to my wireless network. Putting it on wifi isn't going to give it much more bandwidth than having it connected Ethernet with the distance it is away from my 5Ghz router/AP (each is on a different floor) and the level of congestion around me on 2.4Ghz, which is on the same floor (I live in a Condo Complex in uptown Dallas, lots of other wifi routers). The connection between my Fire TV and my switch is ~100Mbps and the connection between my Plex Server is ~1Gbps. I can be moving files betwen my Plex Server and NAS at around 700-800Mbps and still play video on my FireTV from my Plex Server without any issues at it's max bitrate.

SMB is not my problem, I've been using it for a while. The Fire TV has some audio codec/passthrough issues with it's native player. If I switch to SPMC or XBMC and PlexBMC, I can play AC3 5.1 fine straight from my Plex server. I can also select External Player within Plex and play media through any external player such as XBMC without any issues with audio. The problem is that it's a pain to do it that way and it doesn't keep up with watched history, etc. like it should. You also have to manually choose the external player you want to use each time and there are issues with exiting some of them, FF/Rew, etc. The Nexus seems to be able to play my media fine with full AC3 5.1 surround... except it chokes randomly, freezes, etc. and that appears to be related to the wifi. I never said I would be paying for NFS! I will most definitely not be giving Microsoft more of my money to get a simple feature that should have been available in the pro version. As for the free options, I've tried several and they are flaky--so annoying. There is a good NFS server for Windows (Hanewin or something like that) that I've used (and actually run on my moms setup) but I need a client because my NAS does NFS. The free clients I've tried just aren't what they should be, many are dated. The good clients want money.

Ultimately, the fact that the Ethernet port on the FireTV isn't really relevant because that's all that specific port needs to be, I don't have any media with anywhere near a 100Mbps bitrate. Using a switch means that port gets 100% of its bandwidth 100% of the time regardless of what else my network is doing. A lot of people think a switch and a hub are the same thing because they look the same and kind of function the same, but they are quite different. A switch is able to provide each port it's dedicated bandwidth to each other port (traffic is only sent to the port it's designated for) and a hub is totally shared across all ports (traffic from every port is seen by every port). (I'm not suggesting you don't already know this, please don't take offense.) Sorry, I know that's a lot of info, I just want to try to clarify. It's so much easier with a whiteboard! ;) The end result, however, is that something is not right with either the Nexus Player or Plex--I think there are issues with both considering my Nexus Player has issues connecting to my router and both access points and loses connection randomly and that when it is connected, YouTube/Hulu/Netflix all play pretty well. I, also, am not trying to argue--I'm just trying to clarify my situation.

Also, you mention if I have my Plex server on port 3 and multiple clients talking to that port... it's shared. True, but it's a gigabit connection being shared. Unless there are a whole lot of clients communicating with that Plex Server, it's not going to saturate so there should still be plenty of bandwidth for any other Plex client I might have on other ports. It would take 10 Fire TVs each playing close to a 100Mbps (bitrate) media clip to saturate my Plex Server connection (assuming there is nothing else communicating with my Plex server).