I was just about to press the mouse button to purchase a 5 server version of ActiveXperts monitoring application, but had an itch to do a quick google search on 'ActiveXperts Nagios' - one of my favorite ways to find out competitive reviews.
And I found a list of products "suitable for large-scale IT installations and compatible with" a couple products I'd never heard of.
http://www.hw-group.com/software/pd_it_big_en.html
Quick summary of 10 products with their capabilities. Enjoy, someone saved us the time of researching!
