Did you checkout the Spiceworks community? They may have been able to help you get Spiceworks working correctly?
There are lots of things that you can do to speed up Spiceworks.
But yes if Spiceworks doens't work for you I love and use Nagios as well.
After installing Nagios reading ( How to install Nagios on Ubuntu server ) for help (well ok i copied it exactely, I installed NagiosQL ( NagiosQL - www.nagiosql.org ) which helped allow me to configure Nagios though the web without hassle of trying to remember where the files are what they were called.
If you get stuck using nagios, places like Experts Exchange or even the Spiceworks community are there to help you.
p.s. if you use NagiosQL dont tick the N check box on alerts or the contact... it means non so no emails will get sent... i found out the hard way...
Only my 2p
