Does HDD RPM matter?

I’m looking at purchasing another 1+TB internal drive for my computer, with the intent of storing movies (primarily MKV files) for streaming over my wired network to my WD TV Live HD Media Player.  I currently have a 1TB WD 1001FALS as a backup drive, and all my music, movies, and photos are stored on there.  For comparison’s sake, let’s use the WD1001FALS (1TB, 32 MB cache, 7200 RPM) and the WD10EADS (1TB, 32 MB cache, 5400 RPM) as examples.  Is there any advantage to purchasing the 7200 RPM drive over the 5400 RPM drive?

More importantly, is it worth the typically $20 difference in cost to buy a faster drive?  To put it another way, will I actually notice a difference in the playback of movies and the time they take to load, etc. if I were to go with the Caviar Green drive, or is the difference a moot point when factoring in the speed of the network connection?  I’m not familiar with how my network speed would affect anything with the hard drive, but I wouldn’t want to pay for something I essentially will not use.

5400 will be fine its not going to be pulling multiple files rapidly and they run MUCH cooler