If you've got a Streamliner and a Barefaced S12 cab, you've already got (arguably, as all things are on here) a very very good, small, light solution there already. You'll be compromising in at least one way from where you are, IMHO. If your driver is weight and size, you might save a couple of pounds on a smaller head, or possibly ten on the cab, but I really don't see the point (your cabs has wheels?) If you've a bad back, you might be better off putting funds and effort into a lighter bass. A couple of pounds there is much more noticeable - my Dingwall's 7.5lbs, and I can really tell if I use a heavier bass for any length of time.