Ice man what size Powermate are looking at ?
I assume it is for use with your 10" GSO ?
I have the 2" 4x . It's only draw back is weight. They are big!!
I got the 2" 4x and not the 11/4" 2.5 or 5x because I like to place my 2" eyepieces in it and have nice comfortable eye relief viewing with out haveing to glue my eye to small 10mm and under glass .
I also use them with larger UO 11/4"orthoscopics 25 and 18mm for planetary viewing again with out haveing my eye becoming part of the eyepiece.
Just my 2c worth!
Now I know people will say what about all those extra elements---4 of them + the eyepiece elements, but from my experience and that of others there impact is vertually nill on light reduction . There coatings are excellent , and should be for the price.
There is one alternative and that is Harry Siebert has a copy of the Telecentric Powermates at quite a reduction in price. Not sure what his work is like have not been able to find any one in OZ that has one of his products to try before I buy . These are called Ultra Barlows
Keep saving Mark Hodson
http://www.siebertoptics.com/SiebertOptics-barlows.html