WiFi Speed

Hi
I have a Pi 2 with the newest Rasplex installed. WIth that version and the version before I am having lagging issues while streaming HD content from my Plex server (local, gbit network). The lagging varies from constant lagging to once-in-a-while-lagging. I disabled all unneeded services, only SSH, WiFi and Cron are running. When I SSH into my Pi and look under “top” it says “NIC: 75%” (sometimes 85%) while not streaming. When streaming it goes up to 95%. Not sure what exactly that means, but I don’t like it. Running iperf on my Pi as a client gave me this and similar values:

0.0-11.2 sec 2.38 MBytes 1.78 Mbits/sec

And as server gave me this and similar values:

0.0-10.5 sec 20.9 MBytes 16.6 Mbits/sec

The distance to the router is short and my laptop in the same room has no issues streaming movies with extreme high bitrates. It’s not a plex server issue either. My WiFi Dongle is a Edimax EW-7811UN 150Mbps Wireless Nano USB Adapter, which is one of the recommended dongles for the Pi.
Using an ethernet cable is not an option as my connected LEDs start to flicker once I stream something. Thought about using a USB-to-Ethernet cable, but I want to see if I can fix this without buying something (spend quite enough money so far).
What could be the issue here for the really annoying lagging?
Thanks in advance

Edit: Also noticed that SSH is quite laggy most of the time. Everything I type in is shown with a little delay, so it’s def. an issue with the connection coming from the Pi.

Next release has firmware 0.4.1 and new drivers to replace the EOL 0.4 firmware, this may help.

Regards

Okay thank you. I just bough this USB-to-Ethernet cable, but it isn’t working: http://www.bol.com/nl/p/ethernet-naar-usb/9200000047193926/
Are there drivers for this to work or is it just this product that isn’t working?