Things I'd recommend:
CPU: Core i7 920/930 LGA1366 CPU
RAM: 6GB (3x 2GB) DDR3 RAM
Graphics: Radeon 58xx or GeForce GTX470/GTX480, most likely a Radeon because of your price range.
I'd recommend Gigabyte's GA-X58A-UD3R motherboard as it is relatively cheap ($209 for SATA3/USB3 and ultra durable design) and very nice. Anything from Gigabyte or Asus would work great, there are plenty of other good motherboard manufacturers too. Just look for LGA1366 for i7 920/930 compatibility.
As for graphics I really like my Radeon HD 5870, but the card costs $380 upwards (mine was $420) so if you can't stretch your budget go for a Radeon HD 5850 or 5830, if not that you can look at the 5770.
Case really depends on your budget and personal preference, I like the looks of the Antec Nine Hundred but if $100 is too much for a case, I also think Rosewill makes good cases (my server is a newer Rosewill design, cost under $50 and still a really nice case for the price).