Intel I7-980x @ 3.3Ghz
12 GB RAM
ASUS motherboard
Video GE Force 9800GTX+ (rather modest) works well with dual monitors.
Windows 7 - 64 bit
Intel SSD 160 Gb for OS only
Intel SSD for scratch
Data drives 2TB in RAID 1 array, additional data storage swapable 2TB, backup swapable 3TB

I built the above system myself and could not be happier. Speed is phenomenal !

It is used only for photography applications, e.g. PS CS5, LR, PTGUI, HFocus, et. al.

Frequently my file sizes grow to 4 Gb and some stitched files as high as 8 Gb.
Never any problem and PS efficiency consistently at 100%.

- The only drag is saving files to disk. Large files can take several minutes to write, although reading from disk is much faster.