A topbox is a convenient, secure addition to any bike, which keeps its width narrow. And mounting the box at the rear seat position rather than 'out back' on a set of arms keeps the weight in a more balanced position. The Kappa K26 is a rebranded Givi, sized small for mostly urban use, but useful with the addition of panniers for long tours too.
The seatbase to which the box plate is mounted was originally white, and I have repainted it - but I can't guarantee the paint won't flake off! The base is some sort of awesomely-difficult-to-paint plastic (I forget which), and my first two attempts ended in failure. Hopefully, the third attempt, which included a BUNCH of wet sanding, a generous application of adhesion promoter, and 3 coats of high quality PlastiKote enamel, will last - there's about a season's worth of riding on the setup so far without trouble, but you never know.
The box was originally about $75 and the seat cost me about the same, so $60 seems a fair price.