If you would like to show only the quantity field or the select list then you will need some logic to have only one or the other show. If you are using the select list as a set type feature then the quantity would still apply, it would just need to be multiplied by the set number to get the true total price. You would want to alter the total price to have the quantity times this set value times the price for the total price. If you do it this way make sure you leave the set value as a default of 1 for this purpose.
