As a small addition.
The routers the other guys have mentioned, RT-5300 and R8500 etc.. manage their extremely high speed WAN to LAN speeds by having all router functionality turned off.. even NAT is handled outside of the firmware.. via special hardware in the processor to optimise speed.. ie if you actually turn on QoS or firewall or throttling or parental controls or anything at all.. the speed will drop to the same as the Airport. The processor in the routers is simply not capable of 1000mbit throughput without hardware NAT.. this is a special highly optimised hardware NAT built into the processor.. but for most people you want to use a router for its functionality.. and as soon as you turn on anything that works in software ie the firmware QoS for instance.. the hardware optimised NAT has to be turned off.
There is a warning that comes up in the routers when you do this.. telling you that you will cause slow down to the WAN to LAN throughput.
What is impressive is the actual processor you need to run 1000mbps in full router software control.
If you look at PFsense which is a good software router.. FreeBSD based so close to the Airports which are NetBSD.
http://www.firewallhardware.it/en/pfsense_selection_and_sizing.html
A 2.4ghz dual core CPU is only rated to 650mbps throughput.
To get gigabit you need faster rather than more cores.. so 3ghz dual core.
You then get into power and heat as well as cost considerations.
The supplied router is clearly not up the task though. Not if you expect those speeds in any consistent way.
Of course the reality of the internet is that most sites do not have the potential to supply you even 1% of your 1000mbps.. So for most people super high speed internet takes away one roadblock between the customer and the ISP.. without removing all the others.