I'm intending to get the edger this summer, and probably a string trimmer next year. My question is, should I invest in the power multi-head tool and the edger and trimmer attachments, or would I be better off buying the individual edger and trimmer themselves? I think those would be the only attachments I would need right now - I might the pole saw in a few years, if at all. Any pros and cons going either direction? I did notice that the stand-alone edger has a 5.0 battery while the edger attachment has a 2.5 battery - does that make much difference in performance? I'm kind of befuddled here...any advice is greatly appreciated!