I'm using ArcGIS 10 and would like to use various additional libraries that are not included in the delivered version of ArcGIS (esp. numpy and matplotlib). 
First I tried to install them manually as described here: http://matplotlib.sourceforge.net/users/installing.html

But because this seem not to work 

I tried various different mailing lists and forums but so far it seems that this problem cannot be solved; see also my post here: http://gis.stackexchange.com/questions/11376/matplotlib-does-not-work-in-arcgis-10-and-eclipse-python

I'm wondering if it may work if I just install the distribution PYTHON(X,Y) which has all packages I need for development. (see http://www.pythonxy.com/)

Does anyone have experience and knows if I can just install another distribution simply on top of the existing version installed by ArcGIS 10 without loosing my ArcGIS Python functionalities. Maybe someone did even try this and installed the PYTHON(X,Y) distribution to use with ArcGIS already? What version would be best? The newest one runs with Python 2.6.6. 

Thanks! Werner