IBM is bringing free QRadar to a wider audience with Community Edition. Community Edition is a fully-featured version of QRadar that is low memory, low EPS, and includes perpetual license.
I'm already mentioned in my previous article about Traffic Analysis in Qubes OS, that the IDS system alerts and logs should be passed to a log management system where we can correlate them with other logs and alerts. That system can be called SIEM
However a real SIEM system makes sense in an enterprise environment only, because it is requires 7x24 monitoring, and it is also needs special knowledge and experience to analyze the results.