Lets start with power supply
Cooler master extreme 500 W..
Chasis:
A well ventilated big one without PSU and have enough bays for disks:
like this one(coolermaster, thermaltake etc)
http://www.mavibilgisayar.com/ud/4759 CPU:
Core 2 duo E 8400 6 MB cache FSB 1333 mhz 3.0 Ghz
Mobo:
Asus striker II or Asus Maximus or Gigabyte GA45T -Extreme
Disk
Samsung 7200 RPM SATAII with any capacity
or
if more speed is concern Western Digital raptor 10 K RPM (used , no problems but not big difference to fast 7200 RPMs)
Graphics
Nvidia 8500 or more
Monitor
22 to 24 inch LCD depending on budget
but in job where I use dual screens I prefer and OLD 19 CRT as no #1
and LCD as #2 as I can dimm its contrasts much better than LCDs :-/
in home where I use Samsung 22 LCD makes my eyes tired

ps : as my preference..I dont like everything ready..and here with a very small fee they can prepare the system for you under guarantee..
and test it for 24 hours