There is no option to upgrade the video with atom PCs unfortunately, and from what I read ION (Atom = Nvidia GPU) can run content today, but might not later on.
That is the reason I recommend a Core i3. The on CPU GPU is actually quite strong, and what it cannot do the CPU will do, which is very strong as a CPU. And if you have wireless using AES, or encryption using AES, the core i3 will be even better.
Another option is to use an Athlon X4. They are good CPU and are low on power. Not as low as Core i, but low enought to get a system running between 40 and 50 Watts.
The Radeon HD 5450 is a good card for HTPC, and it provides DTS passthru (important if you put a blu ray player and connect the whole system to a receiver using HDMI), but it increases the power concuption by 19 Watts. Still at 60 Watts it is reasonable for the amount of power processing in the computer.
Again...., the H55 might be good enough and it provides the option to add the card later on.
I got the hardware (motherboard and CPU) for my new HTPC
AMD Athlon II X2 245 and a Biostar 790GX micro ATX board.
I will be putting together after I get the RAM, so I can measure how much power it uses. I don't do PVR yet, since I have the recorder from Comcast, but I might look into doing that later on.
The 790Gx has Radeon HD 3300 which is just a step below the HD 5450
http://www.tomshardware.com/reviews/...rt,2088-2.html
I didn't used to be a fan of integrated graphics, but considering how much power you can save, and that they are good enough now a days, and support multiple display, while still giving you the option to add a card later it makes for an easy choice.
My atom PC was built with only 150$ to be used in my car, but I never bought the display, so I have been using it as a HTPC in the mean time