I am also planning to get a new system.
I am just waiting for Intel to deliver the new quad processors in order to get a q9450 instead of the  q6600

The Asus P5K motherboard seem to be quite reliable. I have considered the DDR2 versions of the Asus P5E but found that it had problems with some high end Ram chips
As others pointed out: DDR2 Ram and not DDR3.
I plan to get an Antec P182 box to make the machine as silent as possible
As for the HDs, I initially planned to get a raptor for the system (I have a 36 Gb one currently) and 500 Gig SATA for the data, but found out that some SATA 2 HDs were almost as fast as the Raptor and considerably cheaper. I am considering disks of the Samsung SpinPoint F1 or Seagate Barracuda 7200.11. series These have 32 megs of cache and seem quite popular.

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