You might find that system center essentials is enough for what you need and the size of your company.
SCCM is a behemoth of a product that seems overkill unless you have 100s of servers and 1000s of clients. Essentials is considerably cheaper as well as having a much shallower learning curve and resource requirements. I'm fairly sure I heard that Microsoft won't be releasing any more though, so you might be looking at a dead end product, the last one was 2010
IIRC.
I have heard good things about
Absolute Manage but have never used it personally.
You could of course use multiple products:
Standard build for new desktops/laptops - WDS (Free)
Password policies - Group Policy (Free)
AV and Malware protection/Security - Choose any of the bloated POS that companies install. I hate to say it but I have found SEP to be the best of a bad bunch
Windows Updates/software patching - WSUS (Free)
Hardware inventory - Spiceworks (Free)