Hi citrus,
have you tried
ACCEPT_KEYWORDS="~amd64" emerge wine? I am not 100% sure that the architecture for 64-bit athlons is called amd64, but google suggests so.
There does not seem to
exist an ebuild of wine for amd64, so this might be a problem. I don't know if
ACCEPT_KEYWORDS="~x86" will let you install x86 packages on x86_64 and I have no way to test it. Would be my best guess though.
Also, wine does not seem to work for x86_64 yet. See
this thread for info. Maybe you can build x86 binaries some way, but that's beyond me.
For an overview on how to install masked package see
this page in the gentoo forums.
Hope this helps, good luck,
- drowstar