Your format problems are sadly unsolvable. Adobe DRM and Amazon DRM can't be supported by the same reader due to license issues, effectively forcing you to de-DRM and optionally, depending on the reader, convert one of the two types of files if you want to read them in your prospective device.
I admit I am too happy with my reader, the Pocketbook 360, for not recommending it. It reads DRM'd ePub files, which are used on libraries if I recall correctly. It also features a microSD card slot, which allows cards with up to 64 GB, it is actually incredibly pocketable, and it reads a huge lot of formats, including all the big ones: ePub, fb2, PDF (quite good for text-only PDF's, no good for graphs and/or images since the screen has a size of 5 inches) and Mobi files. Since you obtain Mobi files once you de-DRM Amazon purchases, you don't need to convert them once they're freed.
Ah, and it's e-ink
. Price tag $240, though I recall some sale going on.