I am getting about 54Mbps down and 5-6 up. My service was just "doubled" from 25/5 but the upload is not much better, if at all.
I talked with chat and they did some magic on my modem that did not help. It is an SB6121.
Here is the signals page from the modem.
Here is a shot of speedtest.comcast.net
I had this trouble in the past and there were line issues.
Assistance is appreciated