Do wifi range extenders slow your internet speed?

I stream movies and play games from my xbox one and xbox 360 so i'm thinking of going wired strait into the modem but i wanted to know if i buy range extenders for the rest of my house will it kill off some of the internet speed? even if i'm wired to everything else? I would just be using my laptop and... show more I stream movies and play games from my xbox one and xbox 360 so i'm thinking of going wired strait into the modem but i wanted to know if i buy range extenders for the rest of my house will it kill off some of the internet speed? even if i'm wired to everything else?
I would just be using my laptop and cellphone on the wifi.
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