I would, first of all, recommend taking back that wireless N router and get an 802.11 G router. The N routers have not yet had their specs finalized and some do not work quite as well when scaling back to G or B speeds. The card inside the PS3 is set up to use 802.11B or 802.11 G- you'll see no advantage using an N router.
I would recommend the Linksys WRT54G on a router choice- you would then be able to get a Linksys range extender that you would know for sure would work with the router.