Need Help With A Crossfire Question

Solution
No, you can't, but let's clarify some points:

With AMD you only need them to be from the same series (i.e. you could crossfire one HD7770 with a HD7790 or a HD6850 with a HD6870).

Ideally they should have the same amount of RAM, however if there's no option you could crossfire one gpu with 2GB and another with 1GB, the end result is that they'll only use the least amount of RAM available, in this example 1GB from each.
No, you can't, but let's clarify some points:

With AMD you only need them to be from the same series (i.e. you could crossfire one HD7770 with a HD7790 or a HD6850 with a HD6870).

Ideally they should have the same amount of RAM, however if there's no option you could crossfire one gpu with 2GB and another with 1GB, the end result is that they'll only use the least amount of RAM available, in this example 1GB from each.
 
Solution