Ok this one is pretty and you will be able to move the button with its box all around the page. Just edit the template file tpl_product_info_display.php found in /includes/templates/<templatename>/templates folder of your zen-cart installation.
Cut the code from:
<!–bof Add to Cart Box –>
<!–eof Add to Cart Box–>
and paste it where ever you want. Thats all it takes!