You don't want to stack tuners. It's a terrible idea when the technology is out there to make more power safer and easier for less money. You don't know whats going on under the hood when you stack, it's a gamble basically.
You can buy EFI Live for $799, and then get some really wicked tunes that will put you into the 12's in the 1/4 mile and still be under $1000. Thats not possible if you stack, you'll have less power, crappy power, and will spend more money and put your engine at a much bigger risk of failure.