In reply to ianstevens:
I've only got the Nomad 7, with the plus10 charger, but certainly at the low-power end of the scale, quality of panel is the limiting factor. The goal zero kit in this category is a no-brainer - much of the competition has been completely useless.
I wouldn't be too worried about battery size, but then I'm only using mine for small items - phone, camera batteries, kindle, Nintendo DS (I have kids). I've avoided larger tablets and laptops because I haven't seen any more usefulness in them to outweigh the extra effort.
But I am thinking of getting a 13w panel - or maybe another 7 and, like you, cobbling them together - so I'd be interested in hearing from the techie people.
Martin