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