Hard disk drive speed is VITAL. 10000>7200>5000 RPM. For the 10000 option you would be looking at a western digital VelociRaptor or sorts. I would consider drive speed over capacity, as ultimately the loading times of applications is dependent on the drive speed. Also drive speed is important when backgrounded applications start to get cached to the "page file". Basically the faster the drive the faster the overall perceived system performance. Also don't bother with solid state drives yet, not worth the high price point and lack of performance. In the future they should exceed any manual drive, but not yet. Also to consider the time value of reinstalling an operating system, it is justifiable to choose the right drive the first time, hence if you are going for power 10000 RMP is the only drive to really give you the edge.
Umm no I don't think so. There isn't a 10,000 RPM HDD for a notebook because they require a heat sink, which aren't 9.5 mm anymore with the heat sink attached.
Secondly there are SSD that perform better than the HDD that are out now. They just cost as much as a MB right now. The only real advantage of an SSD now is that they don't use up a lot of energy while they are idle, plus they don't have moving parts and are generally faster in reading, seeking, and writing.
To the OP, I wouldn't buy the 500GB 5400RPM Samsung HDD because it's super slow with the seeking and writing. Plus it uses more energy than some of the 7200 RPM HDDs that are out now.
I wouldn't pay for something that sucks more than a 7200 RPM HDD and drains my batteries faster.
Go with the 320GB 7200RPM HDD by Western Digital or Seagate that are both available for $109 USD at newegg.