Wayne's published FR plots of the new midhorn is with an Alpha 10 driver. Apparantly the 2012 will work just as well with it, but you cant use it in the 8Pi, ported rear chamber output doesn't go deep enough.

The published direct-radiator response curves isn't an indication of how flat it will be in a horn though... but Wayne has said a 2012 will work too, but I don't think that has flux stabalizing rings either(?). I'd suggest the Alpha 10 will sound good though, I know my Alpha 6 horn sounds great and its obviously a non-faraday ring driver.

The low-end is really up to you, there's so many available that will work! I havn't used it, but the 2235's characteristics has always had my eye, goes real deep and in a smaller box than the 18's.

Adrian