My Xbox 360 is upstairs, the router is downstairs. The wireless signal is good on all devices, and the speed, but it's really slow on my Xbox 360, but weirdly has a good. I tried it with a cable, and got much better results, and faster download times. This is not ideal though. I never had a problem with wireless on Sky, and now I have with Virgin Media. It's the Xbox 360 slim with the built in wireless. I tried another Xbox 360, but this had the same problem. As well as that, I'm constantly getting disconnected. It's a Superhub 2ac on 100mb. I'm a new customer, and I don't know what to do from here.
Thanks for posting. I'm sorry to hear that you are experiencing slow speeds on your Xbox 360. Everything looks healthy when checking your connection. For any sort of gaming I would definitely recommend a wired connection over wireless for stability.
If range is the issue for not being able to have a wired connection you can use accessories such as powerline adaptors to overcome this.
I've also included a link here with some advice on improving your wireless connection.