Let's first try to figure out whether you have a wired or wireless issue. Troubleshooting always begins with a wired connection first......since wireless will never be up to speed if Ethernet is not.
If you have not already done this, connect a computer directly to one of the three LAN <--> ports on the AirPort Extreme and run 3-4 Internet speed checks to get an average using one of the popular utilities like www.speedtest.net.
Post back on your results for Test 1.
but I am only getting about 20 mbps through my laptops.
Are you saying that the laptops are connecting using wireless or via a wired connection? What operating systems are installed on the laptops?
If you have not already done so, restart the AirPort Extreme and locate a laptop in the same room with the AirPort Extreme so that it has line-of-sight with the AirPort.....and then run 3-4 Internet speed checks that way to get an average. Post back on your results for Test 2.
Then, move the laptop further away from the AirPort so that there is one wall in the signal path between the laptop and AirPort Express and perform the same checks again. Post back on your results for Test 3.
Finally, move the laptop to the normal location where you will be using it and perform the same checks again. Post back on your results for Test 4.
How many walls or other obstructions like ceilings are there in the signal path between the AirPort Extreme and the laptop in Test 4?
More checks will likely be needed, so you will need to be patient while we work through the process. There are rarely ever any quick fixes with wireless issues.