I've been using an HTPC for about 6 years. I tested all the different software programs before settling on one. For me Sage TV was the best. I recommend you try it out.
One thing to consider is if you will be using the HTPC to record TV or if you are just interested in using the HTPC to playback media. If your interested in recording TV then Sage TV hands down is the best PVR software. Since your looking at the Zotac and it doesn't have a TV tuner I assume your not interested in recording TV.
Assuming that you're just interested in playback I would stay away from those Zotac Ion setups. I've read that they might not have the horse power to run buttery smooth if you don't have the proper codec. Not all videos are encoded properly so if someone else fucks up you want to make sure that you have enough raw computer power to playback 1080p using software rendering.
One of the neat things about Sage is that you can setup a server anywhere in your house and just use extenders to playback in any room. It also has a nice clean interface that looks really professional.
Check out the
screenshots
Here are their awesome extenders
HD Theater. Keep in mind you can just buy the extender and plug it into your network to get all your media.
I personally use this case which can support full size PC cards.
Antec Case. I got mine for $40 in silver. Then I use this
turner to capture HDTV from my cable provider.
Let me know if you have any other questions and I'll try to help.