I'm not familiar with that one in particular, but you're going to be sacrificing quality with those macro attachments. You're much better off going with an extension tube. These are very popular among macro photographers:
http://www.adorama.com/KNAETSDEOS.html. You can probably pick them up used if the price is a little intimidating. Plus, I'm sure there are cheaper brands. There's no glass to intefere with image quality, so what you'd be giving up is build quality and possibly lose your autofocus with cheaper models.