Postgres cpu & memory usage

HI All

    Some more questions from me today again ....

    The client we are looking after wants to look at consolidating all  
their databases onto one Database server.

   Currently they have 16 Servers and a total of 190 Databases running  
on these (even though a lot of them will be removed after the exercise  
leaving about 90 odd).


    They are also running application and web servers on the same  
servers at the moment and the plan is to move all the databases onto  
one central consolidated database.


    However, in order to spec the server required, I need to create a  
report of the system usage from a postgresql point of view.


   I have configured pg_top on all the systems, however the info  
received seems to be incorrect in the following sence:

    - When running pg_top it show the cpu usage as 100% for user  
however when running the linux top command this differs a lot.
     - The linux top command (monitoring all postgres related  
processes) totals not more than 5 % cpu usage and barely 1% memory  
usage.




    I am not sure how to get the correct information for postgresql  
specifically.


   Can anyoneone perhaps assist here?


Regards
Machiel