The extreme is your best bet...The AE is good as a range extender. Another alternative is a Time capsule used with an AE. That's how I deal with all my wifi needs. Almost all ISP supplied routers are C***. I have a net gear from VM, but disabled the wifi, then plugged it into my Time Capsule. I have an AE plugged into the wall socket in the bedroom...range - superb.
You could achieve the same thing with an extreme and will probably find you don't even need the boost of an AE (depending on the size of your home)