New to ATI's Crossfire setup

I've only been exposed to nvidia's SLI modes so now that I'm in the 512 market, I'm looking at the cheaper Crossfire 512 setups.

I understand that
Two cards are required as usual
One of the cards must be a Crossfire
One card does not
Both cards in Crossfire will throttle down to the slowest of the two

Where I get confused is...what constitutes crossfire. Does it actually have to say crossfire in the name of the product (Crossfire master, Crossfire Edition) or does it just have to be compatable with crossfire.

An example is X1900XTX From Zipzoomfly It says Crossfire under the link to manufacturer's Specs...but X1900 Crossfire Edition From Zipzoomfly specifically says crossfire in the name. I've also seen the words Crossfire master

When looking at the spec's, it doesn't seem obvious...to the non ATI
person.

My guess is that there is one card that will control all the features (the Crossfire labeled card....Crossfire edition/crossfire master) that is the primary card and the secondary card is whatever you choose and just feeds into the crossfire.

Wanted to make sure before purchasing. I'm assuming there will be docs on how to set them up. I should be able to buy the two cards above, crossfire them with no problem...and no other combination of ATI/Crossfire would be better (discounting overclocking combos)

What about purchasing 2 Crossfire edition cards...or do you have to buy one crossfire and one of the xtx or xt's?

There is no limitation (other than money and availability) to using 2 Crossfire cards together.

Well according to ATi that's no longer the case. Their recent FAQs (recent as in since the Fall) have updated that information to say that both cards will run at their own clockrates and will share the burden asynchronously.