I've had a whisper 10 for several years as well as it's 40/60 brothers. They are a simple , inexpensive design that can work well if properly maintained.
I HIGHLY recommend a sponge filter on the intake tube...you can take a fat sponge and carefully split a hole in it or..just get a round sponge like the one for a penguin 660R and slip it over your intake tube. This will help keep "garbaahhhge" out of your filter and prolong the life of your impeller.
The sponge filter will also act as an additional biofilter.
for the actual filter element, I usually use just a piece of pantyhose over the frame..tied off on each end. does a nice job of water polishing, too. Well-rinsed, of course!
For those times you do need carbon, I suggest the "Imagine" 12-pack replacements. 12-pack comes with one frame and bio insert, and their carbon is is sewn into the cartridge...not piled at the bottom...and cheaper than whisper brand
--Don