Go the the Ford Focus Fanatics forum. There are people that have torn apart the dash and upgraded the speakers. I remember a very long post where a guy went through every single step for each speaker. I'm pretty sure I referenced that post somewhere on this forum. The ICE and FFE are pretty much that same thing head unit-wise. You're only problem is no space in the back for that Sony sub - you kind of have to do something creative like that person you mentioned.
Your other option might be the FFE shop manual that was available here.
2014 Platinum White FFE (Turning in mid Dec. 2016 25,000 miles)
2013 Ingot Silver FFE
2012 Titanium ICE Focus
2014 Tesla Model S 85