HI Robert,
Either apcupsd or NUT(network ups tools) will work. I've used both and IMO apcupsd often seems to have better support for the newer APC units then NUT does.
That said, I do prefer NUT because I've been using their tools for a lot longer. I also run a mixed shop, APC & Liebert UPS's protecting virtualised CentOS & Windows Server 2003 instances, so NUT's been more flexible for me.