[BDBohnzie]

From my personal experience, Netgear = Crap. But that's besides the point...

20 feet shouldn't make or break anything. Being on the 3rd floor, the signal in your house should be better. Think of the router as an umbrella. The signal casts out then down. So being on the 3rd floor should improve your signal throughout the house.

If your router is having trouble, it might be interference, so I would try changing the channel. Log into the router using the web interface (192.168.?.?) and look for the tab to change the channel. The common channels for routers are 1, 6, and 11. I think the one I have at home, I have set to channel 10 and it works fine. My Linksys Wireless-G Vonage router is on the 3rd floor of our home, and my desktop in the basement gets the signal just fine.

N routers are backwards compatible, so it should work fine with the 360 (purely speculating, since I don't have a 360). As long as the wireless adapter for the 360 is a B or G, then it should work fine with an N router. My sister has the Linksys WRT160 and it's worked flawlessly since she got it.

But if the Netgear router has worked fine, I wouldn't worry about upgrading just yet, unless you have a piece of equipment that can take advantage of the Wireless-N protocol. Wireless-G is just fine, and since most of the time, your signal from Comcast will be less that 16Mbps, no need to faster until you have to.