I had the standard Ford head unit replaced in my C-Max with something similar, but I got the Ford garage to actually do the installation for me.
Unlike you I didn't have the Sony head unit to start with, just the basic Ford one, which was spectacularly awful. Once the head unit had been replaced, it turned out the factory fit speakers weren't as bad as I'd thought they were, it was the terribleness of the head unit that made them sound worse.
Also, what a great car the C-Max was, in fact, just thinking about it now, two of my favourite ever cars have been the C-Max, and now the ST. There's a lot to like about Fords I think.
In fact, I've got a picture of it, because of course I have. (Picture is from April 2010, so a much younger Jnr!)
EDIT - Mine was GHIA spec (this was before Titanium existed IIRC), so you can see digital climate controls and also the heated seat control. It had an electronic parking brake as well.
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