what is a good wireless router

I guess you can connect up to 250 devices to any router that has DHCP or non DCHP(assigning IP)

50 devices is just may be an example. I have not much idea about Apple Airport.

and many other routers can do the same as what it does..

even like AVM routers (europe) they are having built in HD funtions to operate torrents even if PC is off.