Hi Pablo,
If you have the last generation SRW224G4 and not the refreshed version the Cisco SF 300-24 ( p/n SRW224G4-K9-NA) one suggestion could be to use a simple SNMP application such as SNMPc by castle rock or there are plenty of free open source applications if the budget is tight. At least they allow you to monitor. OpenNMS look interesting, but i haven't download the application to see how useful it could be.
Anyway there seems to be many approaches for small business to follow to get access to at least low cost or Open source applications to allow for monitoring of a network.
Hope this post is of use.
regards Dave