It looks like that would work....it could be an issue with the parenthesis. Seems like the first one is out of place and it should be:
<?php if (("".$Categories->getColumnVal("FeatProduct") ."" == "1") && ($Categories->getColumnVal("SpecialOfferPrice") ."" != "" )) { ?>
it could also be simplified to:
<?php if (($Categories->getColumnVal("FeatProduct") == "1") && ($Categories->getColumnVal("SpecialOfferPrice"))) { ?>