In your stylesheet_main.css, find the #cartAdd rule and change right to left:
Code:
#cartAdd {float:left; text-align:center; margin:1em; border:1px solid #AEACA5; padding:1em;}
In your stylesheet.css, delete the #cartAdd {} rule, and add a new rule to keep the next/prev below the add box::
Code:
/* ----------------- ADD TO CART BOX MOVE -------------- */

#cartAdd {position: relative; top: 20em; left:100px;}

.navNextPrevWrapper {clear: both;}