Hi Vivek,
I bought a used Kobo Forma for reading Standard Ebooks, and it's a great experience. That's probably not a suggestion you were looking for, but consider it anyway. If you can appreciate the difference between azw3 and KFX (e.g., the option for ragged-right alignment), I bet you'd further appreciate Standard Ebooks on a Kobo.
If you're like me, you have Kindle books that aren't going anywhere, but I bought a different device anyway, and it was worth it.