A.) I wouldn't go with AMD and those PSUs at all.
B.) There are better builds though $/W should not be considered as per original requirements.
C.) Dual channel memory and cas rating is important in terms of bandwidth and speed which is not benchmarked for.
D.) SSD > HDD on avg, and have better warranties in terms of all components.
E.) 2day shipping should count.
F.) Please see the AMD benchmarks in single channel.
Not going with AMD the power consumption is too high.
The Dual Channel memory is an issue, ideally there would be 2 DIMS rather than 1.
So the machine I would go with is:
Core i7 3.9 Ghz
2GB
$369.78 + $20 USB Stick with Linux on it for HD total $389
From protatech.com
By getting rid of the HD I end up with SSD and I have no need to assemble parts.
So when critiquing the best machine please refer to this machine. Note: technically I was the one to spec it, but azwccc pointed me to the source.