I'm assuming that as an organization you have a lot of vendors that require harmonization and cleansing in order to get good vendor spend analysis. For that purpose MDM would definitely be helpful. I'm working with a few organizations right now that are considering the MDM solution to assist in the exact same purpose. So you seem to be on the right track.
However, the painstaking method is still available via Excel downloads and uploads, which obviously is not a sustainable or recommended choice J.
There is an interesting blog on the ELP network forum on spend analysis. You might want to read it. The blog is application indifferent but nevertheless talks in simple terms about spend analysis & visibility. You can see it here: http://blog.europeanleaders.net/procurement-blog/2007/2/14/avoiding-the-evils-of-the-spend-analysis-debate.html
This was first published in September 2007