Repeated from other VR9000 thread:
Suction in the Powerbot increases almost 40 per cent by omitting the cyclone cup. The cyclone, bagless design, takes a lot of power. It is practical on full size vacuums, but is not appropriate for battery operated robots with limited power. This explains the unimpressive comparisons with other brands in tests. The extra power is wasted.
Besides the sponge filter it is possible to use furnace filter material and tissue replaced every time emptied. Either type is good.
A baffle can be used in place of the cyclone to fill the bin from the end
http://www.robotreviews.com/chat/viewtopic.php?p=135214#p135214