Don't know much about the Dana's other than they might be connected with Swan speakers in some way, which are HiVi speakers produced in China. Although I've heard good things about Swan speakers as value for dollar winners, it looks like a lot of shady marketing with the Dana line, "reviews" in various online forums that all appear to be written by the same guy under different aliases. Maybe they're great values, I have several import products from China that have turned out very well for me. However I'd make sure to listen to a pair before purchase.
Single driver speakers are a whole other ballpark. They are very seductive, but have a few flaws. You can't get fullrange sound without compromises, either beamy treble or rolled off bass. Obviously bigger drivers produce better bass and smaller drivers better treble, the 4" Fostex drivers produce a glorious sound, but slammin' bass drive, not so much. Several manufacturers have gone to using larger full range drivers mated with a supertweeter for fill in. Try Zu or Tekton, and for DIY fullrange I'm sure you've already gone to Planet 10 website, a wonderful resource. For conventional speakers you should check out our own GR Research, Danny is a great guy to deal with.