Sonys are great, but in landscape some people have found it annoying that instead of completely separating pages, it cuts a page into two separate pages (top half and bottom half) and overlaps as you turn a page, so that you will see the same words at the top of bottom half as at the bottom of the top half.
The 650 and 950 differ in landscape mode in that on the 950, you can view 2-page side-by-side mode, like how a real book looks with two pages next to each other, and there is no overlap in that view. The 650 cannot do this. I don't know if you'd want to read pdfs this way, but it is a landscape difference between the two.
Keep in mind that I've heard Sonys aren't all that great with pdfs. They're the best of the major e-ink screens, but if you want to go bigger and LCD you may get a better pdf reader.
Of all your other concerns though, I think a Sony 950 could be closest to perfect for you. It is light, has many dictionaries including Dutch, you can highlight and annotate, is anti-glare, has 3g and wifi and a browser, has a good battery life and has expandable memory. As for text to speech and building table of contents, I don't know.
I hope this reply was satisfactory as a drug.
