The quality of streaming video depends on the connection speed indeed. But there are 2 sides with communication: the sending side and the receiving side. Not all senders will support the max speed you can receive.
It's still a long way to HD-quality via Internet.
All you can do: pay for the extra download speed and cross your fingers that it will have any use.
Presently, I am paying for DSL service whereby I am supposed to get 5 mps on my download. I have tested this, and the very best download speed I have ever gotten, is 2.96 Mps! Because I like to watch news videos, googlevideo, youtube, I find that often, I cannot get a full screen on these, only sometimes I can get fullscreen. Having spoken to my provider, was told what I am getting is great! My son thinks differently! I asked about getting 10 mps but was told this will not give me better video! Would not having a higher DSL speed give me a better video? Yes or No and small explanation would do. Thank you very much!