Dang, I'm sitting here right under the router and I can't get anywhere near that speed. Yet when I test my modem at any test site I get amazing speeds from my computer.
OK....lets solve this. Great speed from the PC, I take it that its wired. That leaves the wireless connection to be at fault. May need to tweak the settings in the wireless settings in the router webpage. Download the app "wifi analyzer". This app will give you the "cleanest" channel to change your router to. If you are on a busy channel like "6" you may need to change to 1 or 14. Check it out
wifi analyzer scrutinizes your wireless connection for optimization