ok so after seeing cataclysm i think i been sucked in the only problem is i already have WoW the game but do i need all of the other expansion sets to play cataclysm also i heard that leveling up is a lot faster is that true

can i play as any of the new classes without cataclysm

I can assure you levelling up is a far faster process than it used to be.

Yep, its faster, more fun and there's more overall story.
 
You can be any choice of race/class except for Blood Elves, Draenei, Goblin or Worgen and Death Knights as long as you only have the base version.
Burning Crusade will add Blood Elves, Draenei and Death Knights, Cataclysm adds Goblins and Worgens.
 
The game is very fun nowadays, more fun then grind so far.

You guys are making it really hard not to jump back in. It sounds so awesome.

i only have BC, but i dont feel like im missing anything, especially at the lower levels.