bjdraw:If your sticking with TiVo then you may like this 3rd party app. Basically what you do is set TiVoToGo to automatically download whatever shows you want to your Media Center. Then with the help of VideoReDo (can probably make DVRMSToolBox work as well for free) it converts the .tivo files to dvr-ms and imports them into media center complete with metadata.
http://tivocommunity.com/tivo-vb/showthread.php?t=359550
Obviously you can't watch live tv and it is limited to non-DRM'd files, but still useful.
Depending on your TiVo commitment, you might be able to sell your TiVos to cover the cost of the DCTs, which can be found online for $200 all day long. Shouldn't take you long to get your money back since you don't have to pay the monthly TiVo fees.
FYI, I had two Series 3 TiVo before I switched to Media Center.
As for a clear QAM tuner. The HDHomeRun is the most popular but runs about $150. The newest is the Avermedia AVerTV Duet PCIe. Dell has it for $65.
http://accessories.us.dell.com/sna/productdetail.aspx?sku=A2837016&cs=19&c=us&l=en&dgc=SS&cid=39715&lid=1003763
Well the two Tivo HDs I have are lifetime so the only cost now would be cablecards which would double or triple with the DCT tuners. Also I would then need to not only go from 4 DCT tuners to 8 unless I do a mix of QAM and DCT and like you said on Fios QAM is limited to locals only. The other issue then is I will need two other devices for accessing the content off the HTPC/DVR since I would no longer have the Tivos.
My plan was for the DVR to go either in my office with my WHS or out in the living room since it will need to be on most of the time for recordings but also to handle the automatic Tivo transfers. Currently I have the automatic transfers on my computer in my bedroom but I would prefer to put that in stand by when I am not actively using it. I wasn't really planning on hooking the new HTPC/DVR to any TV but more accessing it through my current PC, the Tivo HDs, or the 360.
I will probably try the Avermedia Duet then just in the current PC to see if this is truly something I will end up comfortable using that everyone in the house will easily adapt to also. They are still trying to get used to the Tivo HD as it is. I think one of my fears is as long as I have had Tivo I have never missed any recordings and I shudder to think what would happen if someone's show didn't record with the new setup. I just don't want to spend another $1000 or so + cablecard fees on two more Tivos if I can do it cheaper and as reliable on a PC.