Ok, lots to cover

So let’s start at the basic one:

1. If you want CableCARD, you have to choose Windows 7 (you CAN use SageTV however, but Win7 is a must. No linux)
2. Depending on where you live and the type of copy protection from Verizon, the problem with your Central server to other Client HTPC’s idea is Copy Protection. If a lot of what you watch is copy protected, you then won’t be able to watch it ANYWHERE except the server! Which is a problem if that’s not connected to a tv 😉
3. Can you elaborate on why you want Thin-client PCs? Is there something in particular you need them–like browsing?
4. The reason for #3, is because based on your needs, a Windows Media Center Extender may be your best (and most affordable) bet. You could plop some XBox 360’s in each room, and then not only will you be able to share the Guide and recordings anywhere, but it’s a lot less maintenance since you only have to manage the Win7 server itself.

#3 is the biggest question back to you which will establish everything else