Watch the wording on those. The Z says "...with 4 mil SCU Pepper Extract..." so it means there is 4 mil IN IT. Not that it IS 4 mil. Mad Dog does that in a LOT of their sauces. "Made with 6 million SCU extract!!" and you think "WOW!!! That must be insanely hot!" but they only use 2 drops of extract, so it's not bad.
You could try to pick up some 2am. It's about 35 bucks, and I'm pretty sure you can't get much hotter without dropping a lot more coin. But then again, the Demon Ichor is supposed to be just as hot as the 2am.
You haven't said the purpose of this, but I've found recently that straight hab's offer plenty of heat, and better flavor than a LOT of those ultra-hot sauces.
One more idea - It's possible a naga / bhut puree (or concentrate) would be hotter. Ask around here if anyone has some.