Should I or shouldn’t I create an extension using AirPort Extreme routers using 7.9.1 firmware?

I was wondering if there is any advantage installing an additional AirPort Extreme router (7.9.1 firmware) to my network setup with another AirPort Extreme router (7.9.1 firmware) since I get 250-350mb/s download and 25-35mb/s upload?

What do you get when you check speeds in a remote area where you want to use WiFi devices? In other words, do you need a stronger faster WiFi signal in another area of house for your WiFi devices?

If yes, then you can expect the same type of performance from the "extended" AirPort Extreme that you get from your current AirPort Extreme in the general area where the "extended" AirPort Extreme will be located........IF.......the extended Airport Extreme will be connecting using Ethernet to your main AirPort Extreme or to the Ethernet switch.

If you cannot connect the "extended" AirPort Extreme using Ethernet, and must use a wireless connection to connect the second AirPort Extreme to the network, then the speed of the extended AirPort Extreme will be no faster than the WiFi speed in that remote area now. In other words, the extended AirPort cannot increase the speed of the signal that it receives, it can only repeat what it receives. So, while you will have a stronger WiFi signal in the extended area, it will be a slower signal......typically about half the speed or less on average of your main AirPort Extreme.

So please help with ideas if the other router would be negligible extendion if any at all?

We can't even provide a good guess without more information that would tell us more about what you might be missing now that you want to improve.

My house is about 2200 sq ft, all on one level. I have one AirPort Extreme in my office at one end of the house and another near the other side of the house in the den. The den AirPort connects to the network using an Ethernet connection. WiFi speeds and performance are almost identical on both sides of the house.

If I power off the den AirPort as a test, the WiFi devices in that area slow down about 60-70% and some devices will have trouble maintaining a reliable connection to the WiFi network. But, every home is different so your results may vary.

I said in my reply that.......We can't even provide a good guess without more information that would tell us more about what you might be missing now that you want to improve.

You provided more info about your network, but unfortunately you still did not tell us what you might be missing now that you want to improve.

If you are saying that all of the WiFi devices that you mention stay in close proximity to the current AirPort Extreme, then you probably don't need another AirPort in another area of the house.

If no one is complaining about the WiFi signal in another area of the house, then you probably don't need another AirPort unless you simply want to have faster WiFi speeds in an extended area of the house where the second AirPort will be located.