Thanks, and thanks for that last link. I don't know. When you put it that way, that I'm basically just building a blu-ray player with *possibly* some streaming options, a stand alone player makes more sense. But I just bought the case, and drives (both HD and BR DVD) are so cheap right now. The combo is the only thing that's going to cost money.
What kind of "streaming", your own content or the Netflix kind? Streaming (Netflix, Youtube kind) BR play can be had for ~$150-$250 or a PS3 for $300. The lowest end CPU/MB combo's over the AVS forums (noted in a previous post, they are excellent) would run you at least ~$200. The midrange starts ~$350 for the combo. I understand you have the case and drives, but this doesn't look like good money spent to me.
If you plan to do it anyways, go at least mid-range. I don't think you will be happy with the lowest end system like the one linked to. The Atom/ION combo works, but just barely. Many that I have read about just haven't been happy with the performance.
Here is a quote from the AVS HTPC build guide:
The system is essentially the same as the Intel-NVIDIA (iGPU) system with Celeron E3300 replaced by Atom 330. Hence its graphics capability is identical. The CPU is weaker and slower, but good enough for the basic HTPC tasks (video playback through DXVA, navigating Windows Media Center etc.). Here is a performance comparison between Atom 330 and Pentium Dual-Core E2200 2.2GHz 1MB L2 (close to Celeron E3300).
Anandtech CPU comparison
Unless your expectations are very low, I don't think you will be happy with the Atom/ION system. I looked into a few months back and pasted on it, so I certainly am biased.
The lowest cost system at AVS (and the minimum I could recommend) is:
CPU: Core i3 530 2.93GHz LGA1156, $113.
CPU Cooler: Stock cooler, $0.
Motherboard: GIGABYTE GA-H55N-USB3 LGA1156 Intel H55 chipset Mini-ITX, $101. An alternative is Intel DH57JG LGA1156 Intel H57 chipset Mini-ATX, $110.