Undoubtedly there's a more elegant way to do this, but here's something to mess about with:
http://jsfiddle.net/slemmon/ncvhc/
Code:
Ext.define('myPanel', { extend: 'Ext.panel.Panel'
, alias: 'widget.mypanel'
, initComponent: function () {
var me = this;
if (me.subTitle) {
me.title = me.title + '<br><i style="font-size:.8em;color:#C47A02;">' + me.subTitle + '</i>';
}
me.callParent(arguments);
}
});
Ext.widget('mypanel', {
renderTo: Ext.getBody()
, width: 200
, height: 200
, collapsible: true
, title: 'Title'
, subTitle: 'sub-title'
});