Steve, as you know, I'm using the Vampires from DMS, and are more then happy with them.
Not sure if Vampire/Intellect/Demon are all the same, as I also have one set of the Demons, and I don't think its quite as good as the Vampires.
There will be one or two issues you'll have if your still going to be using the Trakpowers, they're not as tall as the Vampires etc, so you'll need someway of holding them in better after you've raised the cell posts to fit the new cells, I know Mr Hubbard is using those hateful Associated thumb screws on his BX, so you could try those.
The other samll issue, is you might ned to change the wiring in the car a little, as the Vampires have the connectors in a slightly different place then the Trakpowers, it'll depend how neat your wiring was to start with
