if you put the pdx on each of them, running 1 of each amp you would want dual 2 ohm subs to wire down to 1 ohm each going to each amp. if you havent bought the pdx 1000.1's i would look for one larger amp, possibly 2kw-2.5kw for 3 of them. 1kw to each is ok, but you can burn up the coils if you put that much to them daily if they're ported (if you dont know what your doing when setting the amp).
buy dual 2's anyways, and series each sub to 4 ohm and parallel all 3 subs down to 1.333ohms, then buy a 1 ohm stable amp around 2-2.5kw.