Since you want to go BIGGER, why not just take the jump now, and go for the M&P 9c, double stack. Lots of bullets, and maybe the ultimate carry gun (concealed). Black stainless, 12+1 in small dress, and bigger mags fit, if wanted. Good size, dependable, accurate, and still reasonably priced.

You still have the little .380 for when hiding is hard, and can always find a single stack 9mm if you really need bigger and smaller together. It'll be easier to buy a middle gun later, than a bigger smallish gun later. MHO.