If you’re saying the transfer rate is 11 megabytes/sec then that works out to be 88 megabits/sec which is a normal throughput for a 100Mbit wired ethernet connection. Highest bitrate you would encounter would be uncompressed Blurays with 40-50 Mbit/s. Everything else has much lower bitrates. So you shouldn’t have any problems. You can test your setup with a high bitrate M2TS bluray file.
I think your cheapo network switch works fine. Even if you upgrade your network to Gigabit (1000Mbit) it won’t make a difference in terms of streaming to WD TV Live since WD TV Live has a 100Mbit port. But if your NAS and your PC have Gigabit ports and you have a gigabit switch then you can transfer files between PC and NAS faster. How much faster depends on your PC and NAS. Probably it’s not worth it since you NAS is not very fast.