To choose the router or upgrade your home network, first you should know what standard you need.
There are three main standards on market now.
Standard Max Speed
802.11g was introduced many years ago, I wrote a post eight years ago related the wireless network.
802.11ac is still a draft standard. It means most products from different company are not same. They may not work together compatibly. The good news is that IEEE will issue the final approved version of 802.11ac the end of this year 2013. Here is the timeline.
The Max Speed described above is in theory. When the router working inside the house, walls, furniture, these kind of obstacles reduce the speed by 50%.
There are also frequence, bandwidth, channel issue for your router.
for 802.11g, 2.4GHz, there are 13 channel. 20MHz each channel
for 802.11n, 2.4GHz or 5GHz, 20MHz each channel, bonding channels.
for 802.11ac, 5GHz,
Bonding channels is double the bandwidth, or 40Mhz. It means faster.
One Key point to choose the right router is to double check the current wifi device in house. The build-in wifi adapter in your laptop, the desktop, the cellphones, xbox etc.
My suggestion is 802.11n is the must have. If the 802.11ac product has 802.11n compatible, you can pick it up. And also make sure the 802.11ac draft can be upgraded to the final version when it is available.