15 or 20 may work, but if the ISP's equipment is as bad as Spectrum and ATT provide, even a higher speed won't help if the device needs more and it can only connect via WiFi. I use Spectrum and hard-wired, my computer speed tests peg the needle immediately- I pay $45/month for 200Mbps. WiFi- I sometimes see 50Mbps with my phone, usually worse. I have used the same app to test speed in other places and seen almost 400Mbps. My Roku (one is a box, one is a stick) units see 8Mbps, after resetting the network and rebooting and it never shows higher speeds, even though they're not far from the router that's in the middle of my place.