Monitors; active or passive?

[Gothboy]

I'd like to get a good set of powered reference monitors for my home project studio. Budget is a bit limited and I'd like to stay in the $299.00 to $399.00 new, range if possible. Some of you will say a good set of monitors can't be had in this price range but I disagree and the budget just won't allow it anyway. It would be great to get a pair with 6.5" woofers but because of price I might have to go with 5". I'm looking at the KRK Rokit RP5, Wharfedale Diamond pro DP82A, Event ALP 5 Active Linear, Event Tuned Reference Biamp TR6, and the Alesis M Active M1 as possibilities. If anyone can recommend any others I missed please feel free.
I don't know much about the difference between active vs. passive though, so this is the basis of my question.....what is the difference aside from passive giving a more flat frequency response. Most of what I do is electronic pop/rock.
I also noticed that most of these monitors use a 1/4" jack for input(the ones I have now are RCA on one end and open wire on the speaker end) so what cable is used to connect my 001 to the speaker....instrument cable or speaker cable?