I have 150/150 from Verizon for $55.
Don't know why they charged you so much.
Faster wifi means a faster modem/router.
AC routers give real wifi speed.
do a google seach on AC router.
Of course, you can have wifi speeds faster than your internet speed but your internet activity will only be as fast as your internet.
Remember that your wifi device also has to have capability that matches your router.
If you have a wifi-G, 54mbps is your best speed.
Once your internet goes above 100Mbps, you must have a Gigabit router to deliver speeds above 100Mbps.
Amazon has some very inexpensive AC USB adapters.
Holla back if you want more info.