I recently found one of my old routers and have been using it for learning the OpenWRT build. Surprisingly the WGT634U has 8MB flash and 32MB ram but I'm thinking it might have too old a CPU for latest trunk and ath9k. I get this impression primarily because LuCI is very slow on it whereas LuCI on the WR1043ND is reasonably quick even without tweaking it.
Anyone guess if a ath9k 5GHz card would work ok or not? I would mod the case to use two antennas if it would work.