What is the speed you are paying for from your service provider? That is often the biggest factor. 

But yes, an AC Router will help. To learn more about AC: http://www.makeuseof.com/tag/everything-need-know-ac-routers/

The speed is determined by the service you have. If you have a anything over 100 Mbps, you'd have to make sure that your modem can support speeds surpassed that, and a router that has a gigabit connection (1000Mbps) AC wireless routers are really good to support speeds passing 100 or more Mbps.

Modems that are 3.0 is what you need to look for.

Thanks for the reply. 

I have 100 down and 10 up, but I ended up getting a Netgear AC 1750 that was on sale for black friday for about $90 USD.

What I was trying to understand was that getting an AC router wouldn't really help you get faster speeds. You'd still get the speeds you are paying for.