You may be able to put something such as DD-WRT on the router and use advanced setting to configure this. I really doubt any consumer grade (below $100) routers will support this right out of the box.
Besides putting custom firmware on the router, the only other ways I think this can be done would be to:
A) Buy wireless adapaters for the devices. I know you can get it for the Xbox, not sure about the STB. If it's DirecTV STB, then I believe you should be able to get one for that aswell.
B ) Run a cable from Router 1 to Router 2 and then plug the devices into Router 2.
C) Flash the router with a custom firmware (although this isn't my strong point)
D) Go with some type of professional grade router that allows this.
I know they make wireless AP repeats, but I've never seen those working in reverse (converting wireless to CAT 5/6) just wireless to wireless and cable to wireless.
Maybe someone else can advise better, but that's the only way I see this working.
Edited by NpaMA, 10 April 2012 - 07:01 PM.