Yes they perform better with the mods (in the order listed) than they do stock (IME). I also found the mods to be VERY easy to do as Pedro mentioned, once you get past "I'm about to drill a hole in my skimmer". I did tear up a feed mod once but fixed it by sending the bit through in reverse at full speed. It heated the plastic and made a nice smooth hole.
Por Ejemplo:
http://www.marinedepot.com/md_viewIt...product=ER1417 http://www.marinedepot.com/md_viewIt...product=ER1613
The recirc option adds $300 to the price tag.