How big is your home?
If you have more devices accessing the router on the upper floor than the 1st floor, then it's recommended to place ian AP up there. Many things can effect WiFi and performance.
Distance and placement is crucial to good operation and coverage. Have a larger home, might just mean that you might need an additional AP to help with coverage, say one down stairs and one up stairs. I've got a 5000sq ft home going online next year, I hope, and will have 3 minimum APs. Normally I run 3 APs in a 2300sq ft home when I'm not testing a single router by itself. I personally don't stream video over Wifi unless it's something like youtube or minor things like that. Netflix and files from my server are streamed via LAN cable only.
I would consider checking your distances from devices to the 655. If there more then say 15-20ft, I would consider getting into an additional AP. Can run on the same SSID and such, just needs to be on a different channel. They work well.