Thanks Matt,
I'm sure you'll appreciate that a specific answer to this question doesn't really exist
Yeh, that's why I made this a discussion post rather than a direct question.
I feel it would be a useful discussion for the Modx community to have.
I'm interested in what other people have done.
Perhaps, as I suggested, we could get people to share what they've done from a basic setup to an optimum setup.
For my own site-
I'm already using the Amazon services plus Couldflare CDN, as well as a minifying script for all css and JS.
My scores on Pagespeed and Yslow are up around 94% (So I shouldn't really complain).
My main issue now is time to first byte which makes up more than half of my total load time.
And that's where things get interesting.
But that's just me.
As I said, I'd really like this to be an open discussion on what people have done and also what challenges people are facing.