I was struggling with this build myself. I have decided against it (will probably just use some sort of media extender with my new build to achieve the same results) but my neighbor who has a similar home entertainment system wants to build one now.
This is what we have looked at:
- XFX MG63Mi7159 LGA 775 NVIDIA GeForce 7150 / nForce 630i HDMI Micro ATX Intel Motherboard
AND (newegg combo)
- Intel Pentium E2180 Allendale 2.0GHz LGA 775 65W Dual-Core Processor Model BX80557E2180
for $125.99 (with a $20 mail-in rebate on top of that)
= $105.99
- CORSAIR 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)
Dual Channel Kit Desktop Memory
$54.99 (with a $30 rebate on top of that)
= $24.99
- Western Digital Caviar Black WD1001FALS 1TB 7200 RPM 32MB Cache SATA 3.0Gb/s Hard Drive
$119.99 x 2
= $239.98
- LG Black Super Multi Blu-ray Disc Burner & HD DVD-ROM Drive SATA Model GGW-H20L
= $249.99
- ASUS EAH3450/DI/256M Radeon HD 3450 256MB 64-bit GDDR2 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Low Profile Video Card /Integrated with HDMI port and HDCP ready
= $29.99
For a case, I personally like the Antec 300 ($59.95) with the Thermaltake Purepower W0100RU 500W ATX 12V 2.0 Power Supply ($59.99 - $25 rebate)
which brings the total to: $820.88 (newegg) which is over what you want.
Not sure if this system works together, but it is currently what we are looking at.
You could drop the blu-ray burner and save $225 that way bringing it to $600. You could use 1 HD (instead of 2) bringing it to $500.
I am not sure how you can get that much lower though.
I've been comparing systems on youtube and eBay as well.
Good luck and let me/us know what you do with!