Fast Internet - Slow Wireless

Hello everyone, I looking to get some advice on wether to purchase a new router or keep my 2nd generation AirPort Extreme. Comcast has just increased my internet speed to 105Mbps at no additional charge. I direct connected my iMac to the modem and tested the speed and I can confirmed that they increased my speed as I'm getting on average 110Mbps down. When I reconnect my 2nd Gen AirPort Extreme to the modem and hard wire my iMac I get similar speeds of 110Mbps. The problem appears to be when I connect to the wireless network the max speed I get is about 40Mbps. Is this a limitation of the 2nd generation AirPort Extreme? Should I update my router to the newest one offered to get the better wireless speeds? Any suggestions would be appreciated.

Regards,

Woody

My current devices that connect to the wireless network are the following:

20" iMac

27" iMac

iPad 2 & 3

2 iPhone 5's

Nexus 5 ( don't judge it's my sons phone)

Apple TV 2nd gen

PS4