Your whole Diagram though is ONLY relevant with the Silicon Dust Tuners.
Ceton has the InfiniTV 6 ETH, which is a networked tuner. They also have a PCI-E version of the 6-tuner setup as well if you want more tuners but would prefer to avoid networking. However, if you want to use it on multiple machines with fairly random usage, I would lean a lot more toward the ETH as it is Ceton's only offering with tuner pooling. The other models can share the tuners,
but you can only setup dedicated shares.
I originally had a 4 PCI-E, and I upgraded to the 6 ETH. It has worked fairly well, but the reviews that complain about it being a little buggy aren't completely off. It ends up getting into this bad state, which makes it unable to tune a channel until you power cycle the device. Unfortunately, there's no way to know that it won't tune until you attempt to do so, which means you could lose a recording. I've owned the device for around a year, and I've had this happen about 3-4 times.
One thing to keep in mind is the biggest downside to these receivers: software support. Microsoft has pretty much cast aside the HTPC enthusiasts, and unfortunately, PlayReady, which is their CableCard DRM, is the
only way to view protected content (premium channels like HBO). To be fair, Windows Media Center does work fairly well, but it still has some pretty annoying bugs and we'll most likely never see updates. Personally, I'd like to see a Metro version or at least some way to help it work a bit more seamlessly with Metro. The problem is that since WMC is a normal application, when you exit the program, it dumps you back to the desktop. Metro serves as a nice HTPC menu, and I'd prefer to go back to it.
EDIT:
Also, note that if you record protected content, it can
only be viewed on the machine
that recorded it. What's worse is when a random show gets flagged as copyright protected for no reason, and you have to watch it on the specific machine. I ran into this problem with certain CBS evening shows a few times. :\