The only way to know is to actually measure the space inside with a tape measure.
Your Envy already came with a GTX 980, correct? That Water Cooled card measures H=28.25 L=266.7 W=149.27 mm, but then you have the water block connection next to it which probably wont fit. Then you have the issue of setting up the water cooling system. How were you going to fit that in also?
That new card takes two 8 pin power connectors. Did your previous card use 8 pin or 6 pin? You need to make sure the psu has the connectors to fit.