Political philosophy

From a number of the websites/blogs I've been reading lately, I've discovered that I need to know more about various political philosophies. Namely, that while I know the general gist of something like Jefferson's view on government, I do not know what is actual argument was. I see such comments as 'noone can argue that taxes are more', I know that its not true. I know that someone had extremely valid arguments for them. But I cannot remember them. I have turned to the
wikipedia for a starting list. I have read some of these before.

So, my reading list is:
Plato's Republic (reread, forgotten much of it)
Aristotle's Politics (again, reread)
Magna Carta
Machiavelli's The Prince (reread)
Locke's Two Treatises of Civil Government
Hobbes' Leviathan
Spinoza's Tractatus Theologico-Politicus
Rousseau's The Social Contract (reread)
Rousseau's Discourse on Inequality
The Federalist Papers
Smith's Wealth of Nations (well, summary of. Its rather dense)
Burke's Thoughts on the Cause of the Present Discontents (I think this is a reread)
Burke's Reflections on the Revolution in France
Paine's Rights of Man
Emerson's The American Scholar
de Tocqueville's Democracy in America (reread)
Mill's On Liberty
Mill's On Representative Government
Max & Engel's Das Kapital (summary, definitely not that masochistic)
Weber's The Protestant Ethic and the Spirit of Capitalism
Galbraith's American Capitalism

Unfortunately, once you get to the 20th century this becomes much more difficult, as everything becomes much more specialized. Economists, political scientists, philosophers all exist in their own arenas, whereas before then they tended to be mixed and dealt across areas. Most early philosophers were mathematicians, but now many eschew mathematics. In addition, there are few major thinkers. There are people who are fantastic minds in their area of specialization, but I haven't heard of any book that changes the notion of how we perceive society or government at anything even approaching the scale of these previous books.