I was going to wait for a big reveal once I made my install thread but since you asked. . .
I have the stock six speaker system with two 12" kicker comp subs. And I have a cheap 1000 watt power bank amp the subs are probably underpowered but they hit way harder than I need them too so I'm happy. Although I have yet to hear them in the mk3 focus because my head unit was a flop. They sounded great in my mk1 zx3 focus though.
I may eventually upgrade my factory speakers but I have higher priority mods on my radar first.