I bought a new 7200RPM drive for my laptop to replace a 4200RPM drive... and to be truthful I don't notice a difference in sound... but I did notice a difference in battery life. It went from about two hours to two minutes... Of course the battery could last longer than 2 mins but for some reason I guess it was pushing the batter too hard and making it think it was almost dead... don't know how that works... but If I use intel's app accelerator and turn down the noise and power settings and set the lcd to turn off after a min of use I can play music in media player for a lengthy period of time....
In short: it basically turned my laptop into a machine that always needs to be plugged in to be able to use it without doing all the crazy stuff to it...
Hopefully your setup will work out better for you.