I'm using a Roku as well these days, and the Plex Media Server does a great job.
The only advantage of using a 5GHz channel is that the router's 2.4GHz connections don't share the same band, so no slow downs occur. Newer models, those that support QOS, don't seem to be affected by streaming.
RE: Plex Media Server--I'll check that out.
I looked at my router settings, and QoS is set disabled. My other choices are Priority Queue or Bandwidth Allocation (which refers to IP ranges, I think). I could try the Priority Queue setting instead of switching the Roku to the 5Ghz frequency. ??
Here's what my router says about QOS:
"Quality of Service (QoS) refers to the capability of a network to provide better service to selected network traffic. The primary goal of QoS is to provide priority including dedicated bandwidth, controlled jitter and latency (required by some real-time and interactive traffic), and improved loss characteristics. Also important is making sure that providing priority for one or more flows does not make other flows fail."
That sounds good, but I never paid attention to QoS when I set the router up. I have NAT and UPnP enabled, and I did some Port Mapping for my network server. Except to make sure I'd enabled specific ports needed for most internet uses, that's about all the advanced settings I touched.