wanted to also add, the netgear R6300 has a transmit power of 720mw and that transmit power is software limited to confirm to FCC standards as the transmit power + the gain of the antenna goes into figuring out the FCC limit on transmit power so technically someone can mod the drivers to use the full of the amplifier and just push out 1584mw+
most wifi amplifier chips can push out power well above the FCC limit, as their market is not just the US which has strong restrictions on wifi.
When it comes to consumer routers, most people buy a wifi enabled box, and plug it in and never touch or look at it until something stops working. So while router makers can add features such as WDS, more extensive QOS controls, it wont do much to the average user who makes up the majority of the market, so the main selling point for routers is range and speed, and a stronger signal allows the router to offer fast speeds along a longer range (eg not getting dialup speeds at the far corner of your house)
So the router makers generally just increase the transmit power and charge more for what is essentially the same transmit hardware with 1 or 2 numbers changed in the wifi drivers.
PS for wifi upload and download connection rates are negotiated separately so at range with a high output router, it is not uncommon to see your wifi radio report a download connect rate of 60+mbit while the upload is only 11 or 5.5 mbit/s and since we download more than we upload, you are likely to get a noticeable performance boost from just increasing the router's transmit power.