Unless you plan on doing imaging, the 4x powermate will be too much for visual use. You simply wouldn't be able to use it on any eyepiece shorter than 20mm focal length, cause it will just give you too much magnification that won't be useable unless conditions are absolutely perfect (1 in a thousand event).
True to a point there Ice.
I use my 4x PM with the ToUcam perfect for that but i also use it for visual planetary with 12.5 18 & 25mm Orthoscopics .
This way I can get the power of a 3.125 ,4.5 and 6.25 mm Orthoscopic eyepiece with out having to make my eyeball part of the optical train.
Of coarse you may have planetary EP's like Radians where you have good eye relief inherent in that design with out having to use a barlow at all.
There is also a 5x in a 11/4" which a lot of planetary observers use as you don't need the the 2"size but the 2"give that little bit more versatility of being able to use low power wide field 2" eyepieces in it.
I use my el cheapo 2" eyepiece like this and it enhances there performance.
A bit of a personal thing and depends on how you use your scope and for what stile of observing you do.
Mark
easy question
