Grey's Anatomy Season 1 - CHECK!!

So I'm definitely a little hooked; however, when I was watching the last episode of season 1, I was like is this really the season finale? But then it did get interesting ;0) Bring it on Season 2! I was shocked though, because I looked up how many discs there were and how much I had to watch to be caught up..season 1 has 2 discs, then I looked at season 2 and there are 6 discs, and season 3 has 7! Holy moly..I'm going to be watching a lot of Grey's! When does season 4 come on? I've read September, but then a couple of ya'll have said not until 2008? Somebody tell me..I've got to get an organized Grey's schedule going..sheesh!