I had that box and was able to get audio with the HDMI on my Samsung DLP. But the only thing i hated was that it would only work on their "digital channels", so I just switched back to some nice component cables.
The 8000 box with DVI actually doesn't work. It says on scientific atlantic's website that the software should update in early 05 witch it still hasn't. Scientific Atlantic just sucks in general
So, I hooked up my 42" Sony plasma today and here's the deal....went down to T-W (Time Warner) and got their SCientific Atlantic 8300HD DVR box. The unit has an HDMI output and the instructions are clear that this will give you both video and audio. Well, it didn't. It only gave a video signal, no audio. Countless calls to T-W resulting in brain dead people giving me contradictory information and it was suggested that the box may be defective, swap it out for another. Another half hour trip to T-W and a new box. Get back home and guess what? Same deal, no audio. When all was said and done I had to wire the box to the TV with component cables. According to a supervisor at T-W they are "working on" supporting the HDMI output (whatever that means) and will have it "supported" at some point in the reasonably near future (whatever that means, again). T-W is a total joke staffed my mentally incompetent automatons who don't care one whit about anyone's complaints. After all, if you want cable, where else are you going to go (if you're in NYC)?
On the plus side, the TV looks gorgeous, as good or better than I recall it in the store. What a great purchase.
End of rant. I just thought I owed it to my fellow NY'ers to let you know not to even bother buying an HDMI cable if you're with T-W.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic