I've got quite a bout of "Shitternet".. new modem?

My internet is completely abysmal. My router is an ASUS RT-N66U and my modem is a Motorola SURFboard SB4200.

Should I call my ISP and have them replace it (Armstrong) or should I just buy a new one from some place like Best Buy or Radioshack?

My speeds on a good day are 12 kb/s.

Strangely on Steam my internet hits 600kb/s. I'm using Firefox with 2 addons and a theme.

 

Step one: check your system for viruses and other software issues interfering with your internet speed.

Step two: reboot your router and modem, if you havn't already, and check the router's settings for anything oddly filtering your connection.

Step three: call up your ISP and have them run a line test. They may need to come out and run a test for shorts in your home's wiring. During this process, also be sure that they're not screwing something up on their end (ISPs do this a lot.)

Step four: if the line test comes out clean, then it would be worth trying to replace the router/modem.