AWStats is free and can be integrated with Helm. Urchin can be run on W2k3, but you can not control it with Helm. WHA has talked about adding Urchin support, but currently, if you choose to use it, you will have to set it up and administer it manually.
I personally hate Urchin, I use to use it on Linux boxes. The best stats package is smarter stats for the $$.