I have the problem with WXSGA+ mode with my rv280 chip. Instead of 1680x1050 I got 1400x1050. But if I use "UseFBDev" option it works fine. Recently I was surprised that this option is gone since some newer version. I would like to check if the driver able to support that mode. Currently I am using version 6.6.3; Could you please unmask some newer versions for AMD64?
There aren't any newer full releases, unfortunately. As soon as a new release comes out, we'll certainly follow the usual process to get it stable. The 6.7.19x ebuilds you can see in the tree are release candidates only and aren't suitable for anyone who doesn't explicitly unmask them.