well having one of my saturn shots feature on Tele Vue's blog this week for using a powermate (5x) i can absolutely confirm they are definitely good for planetary.
what setup have you got Phil?
(scroll down to saturn)
http://televue.com/notamnomen/2020/0...ontent=C2020F3
i also have just a bintel 2" 2x barlow which got me some nice snaps (just not that zoomed in as the 5x). but i'd say going over 2x i would want a nice piece of optics like a powermate.