That's way to much caffeine, even on the back of a
hydroxycut bottle it says "Do not combine with other sources or caffeine" I dunno if it will cause you major harm, personally I wouldn't try it, but more then likely it will cause you to flush out ( itching like crazy everywhere), and/or like allstar said the jitters, and/or keep you up at night.
On another note I assume you already bought the too but if your looking to do both nitric oxide and a fatburner at the same time I would recommend
APS plasmagen stacked with APS phenadrine.