Is it possible to have the option for curly quotes as well (no instead -- would like to have both types available)?

There is no option for this, but you can create a custom script that can apply the quotes with a certain key combination. Create a file called editor.js in /media/jce/js and add the following:

(function() {
	tinyMCE.onAddEditor.add(function (mgr, ed) {
		ed.onKeyUp.add(function(ed, e) {
			if (e.keyCode == 222 && e.shiftKey && e.ctrlKey) {
				ed.execCommand('mceReplaceContent', false, '“{$selection}”');
			}
		});
	});
})();

Then in the editor, select some text, and use CTRL + SHIFT and the double quote key on your keboard to apply the curly quotes to the selected text.