Crossfire with 2 brands card? (ATI 4870)

I was planning to run crossfire in my new system with 2x MSI 4870, however due to time and stock limitation i can only obtain Grandmars 4870, just wondering if later on I add another MSI card to run crossfire will there be any compatibility issue?
and after installing the MSI card, do i need to install another driver?

I have never run SLI/Crossfire before please give me some advice.
many thanks.

The brand shouldn't matter. What you need is similar clock speeds. Even if they are different you should be able to underclock one of them to match. (same with different memory amounts.)

All you need are two of the "same" cards, a CF motherboard, and CF PSU. After that, you simply load the driver and go.

really?? only the stickers..?
i thought their own customised driver would make some differences, or they may have use better components for MSI or ASUS?

When cards first come out, they are always just reference design. No body has had any time to tweak them yet. They slap their own sticker on it, change the bundle, toss in whatever warranty they offer, and out the door it goes. Overclocked models or different coolers don't come till later.