Help me to build c2d for computing

Need to build two computers by the end of Jan. Will mainly use for computing. The statistic programs (SAS, stata, matlab) are very CPU, memory and especially disk demanding. It requires reading and writing large files. I will also do home photo and video editing, and a little gaming on one of the machine. Budget is flexible but I don't need bleeding edge, just want the best performance/price. I will overclock if it can save money. Any advice is greatly appreciated.

case & power: I prefer quiet ones with lots of room to hold several hard drives I have.
mobo: need gigabyte Ethernet.
graphics: I have a 7600GT that I can use for gaming. Need another one with dual DVI (no gaming needed).
mem: 2G each
hard drive: I have a bunch of SATA and PATA ones with PCI IDE cards. May do raid if it can boost performance reading and writing large files.
CPU, h/s: ?

I wish I have the money. No, I am looking for a workstation with overclocking potential. I know SCSI is good for multi-read and write, but heard that some SATA drives nowadays have pretty decent single task speed.