SCCM or SpiceWorks. Even can use Microsoft MAP Toolkit.
What OCS gives you is a snapshot of your environment at a given time. This is useful but it isn't designed to give a historical record of configuration and change. I am currently setting up an iTop server to work with OCS which also contains a helpdesk, CMDB, change management functionality etc. I've come across a couple of minor rough edges with iTop but overall I'm very impressed with it. It is also designed to allow integration with other programs such as OCS and Nagios.
Don't spend money on this type of software until you've checked out the open source alternatives. Products like Sysaid and Spiceworks look pretty slick but you quickly hit limitations with the licensing or get continually bombarded with emails and ads.