Ok so I contacted Sapphire directly about the issue and this is what they have to say (in broken english of course
"That's a special why windows calculate onboard memory, check your CCC it
will tell you that there are 1024mb from the hardware information.
From what I can make of it, it just means that DXdiag uses a different method of calculating memory than CCC. Since a lot of system requirement programs refer to DXdiag (maybe?), it appears that we have less memory than we really do.
So while it sucks that we don't appear to meet system requirements, we actually do.
Maybe Windows will release an update to fix this issue soon. Seems to only happen to HD6XXX cards.