Atom X2 per sec has no problems with HD playback, but the Intel GMA IGP does. Ion is ok. None of your listed builds play BDs. $400 is somewhat stretching it for a BD HTPC build. It can be done.
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quantity of item 1
SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM SATA 3.0Gb/s 3.5
SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
Item #: N82E16822152181
Return Policy: Standard Return Policy
$54.99
select item 2 quantity of item 2
MSI 785GM-E51 AM3 AMD 785G HDMI Micro ATX AMD Motherboard
MSI 785GM-E51 AM3 AMD 785G HDMI Micro ATX AMD Motherboard - Retail
Item #: N82E16813130247
Return Policy: Standard Return Policy
Protect Your Investment (expand for options13-130-247|hide options13-130-247)
Service Net Replacement Extended Warranty Plan
The product will be replaced and shipped directly to you at no charge(more info13-130-247.0.18)
* 1 year: $9.99
* 2 year: $16.99
$79.99
select item 3 quantity of item 3
BFG Tech BFGE450WPSU 450W ATX 12V v2.2 Power Supply
BFG Tech BFGE450WPSU 450W ATX 12V v2.2 Power Supply - Retail
Item #: N82E16817702019
Return Policy: Standard Return Policy
$39.99
select item 4 quantity of item 4
OCZ Gold Edition 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1066 (PC3 8500) Dual Channel Kit Desktop Memory Model OCZ3G10664GK
OCZ Gold Edition 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1066 (PC3 8500) Dual Channel Kit Desktop Memory Model OCZ3G10664GK - Retail
Item #: N82E16820227346
Return Policy: Memory Standard Return Policy
-$14.00 Instant
$89.99
$75.99
select item 5 quantity of item 5
AMD Sempron 140 Sargas 2.7GHz Socket AM3 45W Single-Core Processor Model SDX140HBGQBOX
AMD Sempron 140 Sargas 2.7GHz Socket AM3 45W Single-Core Processor Model SDX140HBGQBOX - Retail
Item #: N82E16819103698
Return Policy: CPU Replacement Only Return Policy
$35.99
select item 6 quantity of item 6
LG Black 8X BD-ROM 16X DVD-ROM 40X CD-ROM SATA Internal Combo LG Blu-ray Reader & 16X LightScribe DVD±R DVD Burner
LG Black 8X BD-ROM 16X DVD-ROM 40X CD-ROM SATA Internal Combo LG Blu-ray Reader & 16X LightScribe DVD±R DVD Burner - Retail
Item #: N82E16827136162
Return Policy: Standard Return Policy
$99.99
Subtotal: $386.94
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You need an ATX or mATX case:
http://www.newegg.com/Store/SubCategory.aspx?SubCategor...
After shipping & tax, it'll be over budget. However, newegg discontinued a $65 LITEON BD/DVD reader. If you don't burn any disks, swap the LG one out for the LITEON. It's available elsewhere.
http://www.amazon.com/LiteOn-4X-BD-ROM-SATA-BULK/dp/B00...
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?Product...