I don't feel the need for one personally. I syphon from the main FV into a second FV which is fitted with tap and add priming sugar to that. This leaves the vast bulk of the crud behind and then bottle/keg. Leave for three to four weeks and the beer's always pretty clear. The yeast strain makes the biggest difference in my opinion, e.g. US05 doesn't pack down as tightly and stick in the same way as S04.