Have you tried OpsView? They package up Nagios with an easy installer and nice UI. Graphing gets enabled by default. It's all very slick and easy. I've used it a couple times and it makes Nagios a far better system. OpsView is mainly open source, though they have a commercial edition with extra features
Nope. Never seemed appealing to me, as I have easily installed Nagios with the graphing plugins and other added features in the past by hand - for a few companies at least.
One of the biggest wins of Icinga2 for Nagios shops is the fact that it can be sort of retrofitted to work with your existing Nagios hosts using NRPE.
Of course, NRPE is highly insecure and this is not recommended, blah blah, but it works, and I'm sure there are more than just a few people still using and older version of NRPE in production.
If you are worried about spending money when expanding to 26 hosts, you aren't their market anyway. If you're worried about spending a few grand on monitoring for around ~100 hosts or more, then you have a very strange business model.
