CDN solution for multisite

I'm looking to implement a CDN solution for my multisite install to get things moving faster. I've read different articles and it seems like there a dozen solutions out there. Is any one simpler than the other. What about the Dropbox solution I've been hearing about, is that one any good?

I've setup CDN before using W3 total cache, but only for my main site since it doesn't support multisite, but I don't see any reason why the subsites shouldn't get the benefit too.

I'd love to get some input on this from others.

EDIT:
I should add that I'm using Quick Cache as my caching pluging - I've read that some CDN plugins require specific caching plugins to be installed.