Yes they would probably be happier if there was 2, but i have just one and as long as we give her lots of cuddles she is great. But i still think it would be better to have two if you can afford it (they eat TONS!!)..
We bought our yellow lab 10 weeks after buying a golden retriever, and although they are a handful for the first few months it has been easier in terms of spending their energy. Not to mention the entertainment the we have gotten from both of them together, but watch for jealousy issues. They could arise, and feed them seperately.