Kenko extention tube (7 photos)

Could you tell me something about the minimum and maximum focus distances with your lenses? I have been wondering about getting the Kenko extension tubes but, while people often talk about the working distance, I am interested in the range of distances that you can focus on when using the tubes.

It's a question of whether I get the extension tubes or go the whole hog and get a 60mm macro lens which appears to be very good. At the moment, I use a close up lens (500D) and I hate taking it on and off and frequently drop it when I'm in hurry! The 500D gives a focusing range of about 300-500mm. If the tubes had a larger maximum focus range, I would be tempted to get them.

Thanks.