Oh, be carful Nigel McN, there are some rabid MST3K haters on the forum who would pop a main cable in their flesh bucket if they thought you were suggesting watching these "classics" in their bastardized, cruel & disrespectful MST3K versions.
It's been mentioned a few times, but since the title specified DVD's...The Ultimate Matrix Collection contains a disc just about 1) philosophy and 2) the science.
The extras are voluminous and worthwhile for a sci-fi fan.