There's actually a stick at the top of this forum called "Determining Hard Drive Performance" written by a complete genius () which should answer some of your questions.
http://www.sharkyforums.com/showthread.php?t=268718

You have a lot of the information already above. Your list of hard drive interfaces and spindle speeds is complete.

To answer your question about cache, it's like short term memory (RAM) on the hard drive to help with the latency associated with hard drives. Hard drives are so much slower than the rest of your system that every time your system needs to access the hard drive it comes to a screeching halt (in computer time at least), so the cache tries to prevent that allowing the system to write to high speed cache which in turn writes to the drive on it's own time.