Apparently the n900 is also known as the wndr4700 and it can run wds the same as my wndr3700. However i was under the impression that can only be done between 2 netgear routers - I never bothered trying it as I really only use the wndr3700 for streaming to a Vizio tv.
The device that you say is slower is connected wirelessly to the n900 or via ethernet?. If it is connected wirelessly is the n900 set up wityh the same ssid? wep security? no security? both radios on or only one? How exactly is the n900 connected to the rest of the network? Sorry, I just find it confusing as I wasn't aware that you could repeat from a non-netgear base router.