my C drive is a Samsung HD 103SJ 1Tb, it reaches about 100mb/sec
So I'd see a good performance gain
my D is two Seagate Barracuda St3500320AS 500Gb just like yours but setup in raid1 (i think, they act as one big 1tb drive) using the disk management tool in windows. (software based raid)
The two of them reaches about 160mb/sec configured like this.