Ok guy and gals I will maybe let you know some nice stuff to know about cable internet. If you have a house make sure the cable is RG6. Do not use splitters from Homedepot, Walmarts and like store. I use comiscope or autronic. splitters. Some cable companies you can to service centers and pick one up for free.
I have the Comcast 105 down and 20 up speed tier. My speed readings. above 115 down and 22 up.
if your are well below what you are paying for then you are having problems. Call for tech to come out and test the connection. You can got this site and go the correct forum and they can help you out.
http://www.dslreports.com/forums/all
Here is the Faqs about what your modem levels should read
http://www.dslreports.com/faq/9737
I beleive the Receive/Downstream: -15dbmV to +15dbmV should be +10 to -10.