Hey, im soon to be getting a sub (or subs

) for my Mini Clubman (a classic one), and ive got a few questions about them, would be great if anyone could help me out.
If i have a 2000w sub, do i need a 2000w amp?
or, if i have a box with 2 subs, total 600w RMS/2000w Max, will this 1200w amp power them without blowing up?
Which is better, a sub with a built in amp, or a separate amp?
And does the power supply go via the head unit, or direct from the fusebox?
Oh and do you think a Mini has enough power to run a setup like the ones suggested above?
Thanks, James.