did your card come with a DVI to HDMI adapter? Most (if not all) AMD cards output Audio through the DVI connector when using the DVI to HDMI adapter. Before you spend a bunch of money on a new card give it a try!
I call BS on a firmware update adding input lag. Sony is well aware that one of the reasons this TV is desirable is because of the low input lag. If you visit their online shop, they even mention that the "W" series is best for gamers.
I can't wait until this technology is implemented in AVRs. I currently watch most of my movies and games with headphones and I use yamaha's silent cinema which is pretty good but this dts stuff is definitely the next level.