Are XML databases good for small to medium non-programming business project management?

Question

Last couple of weeks I've been searching for some project management solution for a place where I work at the moment.

There we rely on excel spreadsheets, but we meet limitations like access rights and concurrency (I have to work with a local copy of a spreadsheet and twice a day dump it to the main spreadsheet) and software versions compatibility (some people have the latest office, some have 2003).

Redmine was the closest, but it really does not meet our needs - excel spreadsheets suck, but they have some stats tools, and anyone can edit them without any extra learning.

Now, not to be immediately (or at all) proposed to use in production, but rather as a proof of concept, I would like to play with OODBMS or XML DB on my spare time, to make a web app for managing repetitive tasks which can however vary, for a group of 5-10 people, to be used not instead of 'serious' solutions, but maybe along with them.

So I wonder, would these DB management systems work here or should I learn relational databases and ORM in details instead of wasting my time with these? Would they allow to clone existing workflows descriptions and fine tune them for another task? Would they be difficult to maintain?