How about N.reinwardtiana?  It's similar to N.alata, though it
has fancier shape.  Or N.sanguinea?  If it's speed of growth
you really want, then how about some hybrids?  N.splendiana is
a very nice cross.  Any hybrid with at least half the parentage
of highland origin should do good for you and grow quickier than
almost any species.
  Hey Nepenthephiles, I enjoy thinking up possible hybrids
like N.rajah * N.rafflesiana.  What fantasy hybrids are out
there in your minds?  Perry mentioned the N.rajah * burbidgeae
that I was unaware of, talk about fantasies coming true. :)
N.clipeata * N.lowii?  I'm not so sure of that one, it's real
mind bender trying figure out what it might look like.
Dave Evans