After a bit of research, and several glowing reviews, I just ordered the Hitachi 7K3000 1.5TB hard drive. I will be using it as my system drive (and I'm tempted to order another pair to stripe as my video drive for editing). Benchmarks show this drive is fast! I'll be short stroking the drive (probably down to 200GB) to get even faster OS boot times and program launch times.
Two of these drives would cost you just a tiny bit more than $150.
Before being turned onto the Hitachi 7K3000 I had also considered WD Caviar Black, but they are more pricey and many benchmarks show the 7K3000 is right on par with the Caviar Black.