A lot of this was covered already.
There is no difference between SATA and IDE, except burst rate, which is directly related to the relatively small cache size, and some (becoming more everyday) SSD drives. It's not the the SATA bandwidth but the fact that your drive is old and slow.
Your 7200.7 has an average read of ~45MB/sec. the 640AAKS has an average read of ~90MB/sec. This is due primarily to PMR (Perpendicular Magnetic Recording).
So you will double your speed and that will most definitely be noticeable.
You would see no performance increase, except burst rate, if the 6400AAKS was a PATA drive, because it would not be outrunning the bandwidth PATA provides.