Issues getting the full speed for the gigablast

What you have in your home does not matter If the lines, transmission equipment, web sites, services, businesses providing the signals to your house can't handle the speed of the services you are paying for by the time it gets to your home. Also consider how many devices are being concurrently being used  and for what at the time on your home network which affects total bandwidth being used.  Unfortunate but the truth.  That's why if you read between the lines from many ISPs it says "up to".  They do not provide a solid guarantee.