Case: Silverstone GD05B (99.99)
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163166&Tpk=silverstone%20gd05
A solid receiver-form factor case. Includes 3 80mm fans and has space for two additional 60mm fans. The optical drive bracket is above the motherboard, which limits the size of aftermarket coolers. Aftermarket cooler doesn’t really seem to be necessary.
CPU: Athlon II X3 440 (74.99)
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103843&cm_re=athlon_ii_x3-_-19-103-843-_-Product
Enough power to handle encoding tasks as you move your collection to your hard drive(s).
RAM: GSkill 4GB kit (76.99)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231396&cm_re=ddr3_1333-_-20-231-396-_-Product
More than enough for an htpc.
Optical Drive: BD-ROM (59.99)
http://www.newegg.com/Product/Product.aspx?Item=N82E16827135205&cm_re=blu_ray_drive-_-27-135-205-_-Product
Go cheap and OEM. Don’t forget an extra SATA cable and your BD playback software (TMT3, $59.99, http://www.newegg.com/Product/Product.aspx?Item=N82E168170034200SF $40 cheaper than buying it directly from Arcsoft. Make sure to download the trial version to make sure you like it.)
Hard Drives: 2 Samsung F3s, 1 TB (74.99x2 / 149.98; available for ~60 with code until 9/6))
http://www.newegg.com/Product/Product.aspx?Item=N82E16822152185&cm_re=samsung_f3-_-22-152-185-_-Product
The consensus choice on Tom’s. In fact, go ahead and get two. You’ll need the space to transfer your Blu-Rays to the hard drive.
Video Card: MSI 5570 (84.99 / 69.99 after rebate)
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127481&cm_re=5570-_-14-127-481-_-Product
Handles full suite of post processing abilities (http://www.anandtech.com/show/3601/the-final-word-on-the-best-radeon-htpc-card ).
Really, a video card is optional, unless you want TrueHD sound, which requires an HDMI input on your receiver. The on-board 4200/4250 is more than enough to handle Blu-Ray.
PSU: OCZ ModXstream Pro (59.99 /39.99 after rebate)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341016
A modular PSU isn’t a requirement for an HTPC, but it does make things easier.
Motherboard: MSI 88GM-E43 (79.99)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813130293
A solid motherboard that has given me no problems.
However, if you’ll be plugging into a receiver without HDMI passthrough, then you want a motherboard with S/PDIF, since the brackets are difficult to track down. In that case, go with the ASUS M4A785TD-M EVO AM3 (79.99)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131406
Total Cost: 686.91 (636.91 with rebates; 566.92 without video card; sub 500 if you start with one hard drive)
Of course, chances are you still need an OS (100 for Win 7 Pro), a 10ft interface keyboard (50-150), Blu Ray playback software (60), 2 extra SATA cables if you don’t have them laying around, and possibly a remote (use a $5 dollar program for your smart phone as a temporary workaround if nothing else).