Hi SupaRice,
You most likely will have this sorted now, but for anybody else who has a similar idea I shall answer anyway.
For products such as RSA EnVision, ArcSight, Huntsman, Q1 etc they do not offer any OpenSource stuff, or offer any demos / trial due to the fact they take a lot of time to setup and will only supply with recommended hardware etc
A good starting point that I would suggest, as in fact I did also, First of all I would download and install Security Onion which is a Linux distro the comes with SNORT / BroIDS / OSSEC and many other OpenSource software packages are installed,