The 50 F1.7 would work fine on a Sony Alpha. The Sigma 60-200 may not. Some of the older sigma lenses need to be re-chipped for the Auto Focus to work on the DSLR's. My suggestion would be to head over to the lens database at dyxum.com and do a search on the lens.
While the 50 F1.7 is a pretty good lens (some hate the Bokeh on it), they are a very common lens, probably worth about $150 (unless they are the maxxum version with the crossed xx's. These are a little rarer and worth a little bit more if in excellent condition).
But don't let me put you off. I entered into the Sony system with only 2 kit lenses and the 50. Now I have quite a few more, including the excellent Beercan (70-210 F4) and am very happy with them.
edit - sorry, it appears that you have found dyxum. Considering that the lens is not in the d/base, I would say its a non starter