As I am Planning to built an application for client company with a current customer base of 500 following scenario:
At any given time at least 450+ logged-in user will be participating in the various web service provided by the company.
The number of Request will very from 450 to 8 times the logged in user.
Zend framework1.6 handles 53 request per sec
prado handles 60-80 request per sec
yii handles 400 request per sec
symphony handles 50-90 request per sec.
(*above data is collected from some web resources)

what about Modx?
Please give me answer in urgent as i find modx much better as it requires less learning overhead,reusable component and maximum output in minimum time compared to others.