which router should i buy

Do you mean a real cisco router or the things they sold off to belkin that used to be linksys.

It also depends what you mean be capable of 1000 devices. You mean a place to plug them in or traffic rating.? Even the smaller cisco routers can pass the traffic for 1000 devices ...it is much more important the total bandwidth used rather than the number of users. If you are looking for switch ports only thing that large is the 6500 series switches. You would have to use bunches of smaller ones if you did not go with a 6500