[lsiberian]

Tweeters are generally padded down because they are inherantly more efficient than woofers. There are some efficient full range drivers, but they have rediculously low xmax and therefore cancel out any gains obtained from the efficiency gains.
Multi-driver is the way to go if youre looking for SPL.

The bigger the better also, but if you're using a sub you can sacrifice extension for efficiency...

Agreed. I know of no full range driver except maybe the Infinity MRS that is capable of high volume. Full rangers are more suited to surrounds IMO. You need less SPL in that application.

 

[lsiberian]

Make sure you keep us posted on your progress. I'd also ask that you document this build via photos.