help buying cube

[Gladys Pérez-Almiroty]

hi:
a very dear friend wants to give her husband a cube top of the line. i 
have thought of putting the max ram, a 7200 hd, but do not know about 
the processor and the video card.
could somebody help me? i was looking at the 1.2 mghz processor 
upgrade, but do not know its pros and cons. what about the video card? 
any recommendations?
can yo put a superdrive that works with idvd on the cube? i read 
somewhere that you could. am i mistaken?
i need to do this without his knowledge so the decision will be mine 
and i want to do it asap.
thanks for your help!
gladys