Intel Core i7 920 (4-core/8-threads) socket 1366 with (3x) 2GB triple channel DDR3-1333. Pretty much any Intel X58 motherboard will suffice, I like the Gigabyte mobo's because the Intel SATA Raid 1 is easy to configure, component quality is good and features are plentiful. Key feature right now is USB3.0 and SATAIII inclusion - USB3.0 in particular, don't buy a motherboard without this. Gigabyte GA-X58A-UD3R mobo fits the bill for non-overclocking workstation tasks, but I'm not sure it's available just yet.
For hard drive... anything SATA 1.5TB or 2TB in RAID 1 is good, WD or Seagate. No RAID if you want to save $$. 2TB Seagate Barracuda XTs are SATA III and would give the best performance possible right now. I would not recommend SSD, if it dies you loose all info, there's no recovery.
ODD are cheap and all the same... get BlueRay DVD burner in SATA. Doesn't matter who makes it.
PSU - minimum 750W "80+ Rated" at least, Seasonic and PC Power and Cooling are good MFGR.
VGA - ATI is better right now. A pair of ASUS Radeon HD 4770's in crossfire will give you four DVI/VGA outputs for your displays. It's a mainstream card, but fine value for non-intensive-gaming application and can handle 24" resolution/HDCP. I haven't played with the Radeon HD 5770's but from what I've seen they are DVI+DVI+HDMI+DisplayPort, so you may be able to run three monitors off just one card... check ATI website for that detail - either 5770 or 4770 (in pair) will work for three-display set up.
Core i7 920 - $315 (canada comp)
Gigabyte GA-X58A-UD3R - est $300 (not sure where avail yet tho)
PSU min 750W - est $150-200
(x2) ASUS Radeon HD 4770 PCI Express x16 - $120-135 each.
HDD - min 2TB SATA, preferably RAID 1 2TB Seagate Barracuda XTs - $350 ea. or WD Caviar Black 2TB (64MB cache, 7200RPM) ($350)
Option two - mainstream biz friendly:
Intel Core i5 750 (socket 1156, 4-core/4-thread, 2.66Ghz, 8MB L3 Cache, 45nm) ($234) and Gigabyte GA-P55A-UD4P motherboard ($194) and (2x) 2GB DDR3-1333 at least. Dito from above for VGA, PSU, ODD, HDD, etc.
For OS, run Windows 7 Ultimate 32-bit (64-bit if you want to track down 64-bit applications and drivers (still somewhat spotty).
The Virtual Machine app inside Win 7 will allow you to run Win Vista, Win XP, etc. for any software that has a problem with Win 7.
