I've got a router with built-in DSL modem from Draytek. It's "only" 100 Mbit and doesn't do 5GHz, but it wasn't too spendy and people on this board have spoken highly of Draytek. 1.5 years after buying mine, it's still working fine, whereas the Netgear boxes I'd bought previously only lasted 6-12 months before having heat-induced early death problems.

I disabled the Draytek's internal wireless and plugged it into one of the Airport Extremes. My builder was smart/lucky enough to have run Cat5e wire from all the outlets to a central closet, where I have the router, so I'm using one of those runs as a GigE line to the second Airport Extreme, which is parked in my home theater where it both provides WiFi and acts as a switch to connect the TiVo and other gear in the rack.

(Previously, the downstairs duty was covered with a D-Link 1522, which died from heat issues, and I replaced that with a cheap Asus router that could run in AP mode. That was again having problems, and is now replaced with the Airport Extreme.)

The closet is upstairs in one corner of the house. The home theater is downstairs in the other corner. The two Airport Extremes, together, seem to be doing a fine job of covering the house.

As you might imagine, I'm now increasingly sensitive to whether my network gear has been engineered with heat in mind. When I saw the iFixit teardown with a sizable heat sink attached to the control board, and a fan attached to the power supply, I concluded that Apple's new hardware was worth the price premium. We'll see how that pans out.