AC1750 / C6300 most recommended wireless extender

Hello all, our cable modem and wireless router are hooked up in our Basement - we have a very large house and so our internet cuts in and out while we are upstairs or outside.  I work from home so this is extremely important that I have the full range.  Which wireless extender will fit this model the best?  Looking to plug something in on the main floor so that it would reach both the lower basement and the upper level.  Office is on the main floor.  Thank you kindly for your help and expertise!