You did not link any particular asus routers. The asus routers in general are some of the best on the market.
In general unless you have some very old crap router it will not likely be faster. You are limited by your ISP. If you only have a 25m internet connection it will still run 25m no matter if you use a 64m router or one that can run 450m.
You also need to ensure all your devices also can run 802.11n. To get optimum speed out of a 802.11n you really want to disable the support for older devices like 802.11b or 802.11g. If you can not you are likely best off keeping your old router to run just the older stuff and move all your more advanced devices to the new router.
For $100 you can get a very nice dual band router...