Wireless N Router

This may sound like a stupid question because I can't see the forest for the trees, but I can't locate this answer before shopping. My question is this: I currently have a Linksys g router in my home. I have a printer (wired), two laptops and a desktop computers and a wii linked to this. Until recently, all has gone very well. Lately however, the system seems very slow on any computer (range 6yrs to 3 mos in age). I have noticed the light panel in the front is no longer white but orange. I usually believe that this is a firmware update that is needed. I have checked and all states that I am on the most current version. What else could be causing this? I have also thought that maybe it is time for a new router in any event as this one is a few years old as well. I wanted to get an N wireless router hoping for better range. Second floor and third floor is spotty. My question with regard to this is: all n router that I have looked at state they support b/g/n. Does this mean that I do not have to also buy a network adapter for the older computer that only has b/g? Recommendations? Work with old one or go for the new one???? Any thoughts would be appreciated. Thank you.

I just replaced my old Dell 2350 Wireless B/G router with a Belkin N450 Wireless N Gigabit router. That gives both of my Ethernet connected computers Gigabit speed while my laptop still connects at 54Mbs (G), so you will not have to upgrade your older computers.

I live in a very rural area where I have had more success with linksys than belkin or netgear. Any suggestions with that company?

All the newer routers seem to work well from what I've read but I have no personal experience with any other than the two I mentioned. All N routers I've read about are backward compatible with B and G so which ever you choose will not cause a problem in that regard.