Now on to the topic. If you are using digital cable, the only current supported tuner/capture device is the Silicon Dust HD Homerun:http://www.newegg.com/Product/Product.aspx?Item=N82E16815327005&Tpk=hd%20homerun
Now if you want your pay channels, like HBO, or Showtime and the lot, then you will need one of the one's you mentioned as they require a box for decryption.
I use 3 Hauppagge PVR 150 cards. Two of them are hooked up to Dish Network Satellite receivers, and the third is hooked up to my Roku Netflix Player.
I use a USB-UIRT to control all of it http://www.usbuirt.com/order.htm
, and this, as far as I am concerned, is the best addition to my system, I currently have 3. They can learn any IR remote, and can control anything you can teach it. And it is plug and play.
However in these days of limited PCI slots, a better choice for a capture/tuner card will be a PVR500, they have 2 tuners, and with the addition of a fairly inexpensive add-on riser (its like $15US) you can have 2 A/V capture sources. This like the PVR150 its' an analog card, so digital cable is a no-go for a coax connection, but they have S-Video - Composite - and Red/White audio hookups for your set top box (back to the whole HBO/Showtime lot) and can capture the output of your cable box, and with the USB-UIRT control the channel changing.
So, to sum up:
If you have digital cable, and don't pay for any special channels that would require a box for de-encrytpion, then the Silicon Dust HD Homerun dual tuner (coax connection) device is for you.
If you have pay channels (HBO and the lot) that require a box, PVR150 or PVR500 cards are the way to go.
Both of the above options are plug-n-pray with LMCE, and configured for you by the system.
For the mythtv and livetv functions, you will need a channles.conf file or a subscription to http://www.schedulesdirect.org/
for your program guide info. This is a subscription of $20US a year, and provides for US as well as Canadian programming info.
Best of Luck To You,