Most of the replies here presuppose some duty to help the poor, the elderly, or the underprivileged. Keep in mind, if you are a tax paying citizen of the United States, you already are helping these individuals. Our government is taking your money by force and giving it to them.
I am not my brother's, or sister's, keeper. As I am able to perform the actions necessary to sustain my own life and happiness, so I recognize in every individual the ability to do the same. As I do not sacrifice myself for others, I do not ask any one to sacrifice their self for me. I do not see the world as a helpless, degenerate mass of people crying out for help, but as a benevolent, rational world in which I am free to trade with rational people, value for value. If you trade $20k for SRS, is it a fair trade? What if you trade $20k to a boozing alcoholic whose mind has rotted away years ago? What value, other than assuaging an unearned and underserved guilt, do you gain?
There is a difference between being generous or benevolent, and being self-sacrificial. Whether you earn $20k through honest work, inherit it, or win it in a lotto game, it is yours by right and you have a moral right to dispense with your money as you wish.