From what I know, I dont think the dir-655 ever slows down. And there are two ways you can talk about the slowing down thing,
1. If you are transferring files from one computer to another, the fastest is by using hard wire since its 1000mbps compared to 300mbps wirelessly.
2. If you are worried about internet speed, the QoS engine will kick in.
The QoS engine has a brain in which gives priority to which ever needs more bandwidth speeds.
As a conslusion, youre good both ways. I dont think you will have a problem of slowing down.
(if the computer is near the router, youre better off hooking it with a hard wire IMO)
hope this helps!
