Syncing Calibre Library & Page over Andriod and IOS

[DiscipleofNagash]

Hi,

I am not sure if this has been asked, but I couldn't find it.

My current setup is:

Calibre Library on home PC > files stored on hard drive.

To read:

Email .mobi to kindle account.
Use Kindle app on Android Phone and Ipad to read (chosen for whispersync).

Now this does work pretty well. However one annoying thing is that if I update something in my library, then I then have to mess around in my Amazon account looking for the file I previously emailed, delete it, and then resend.

Ideally what I would like is to have the library held in the cloud, which I could do via Dropbox as I have a 40GB account with them.

I assume I could relocate my calibre database on my PC to the dropbox folder, however are they any suitable apps that could connect to this database on an Android device / Ipad, and also sync to the last page read.

Or is there a better way to do this? Any info would be much appreciated.

Also a couple of easier queries

Is there a way to show a book is unread?
Is there a way to put comments next to a book?

Many thanks