Modern Mini DisplayPort to HDMI adapters and cables do support both audio and video.
Because they are Passive, not Active, then don't work when three displays are connected to one card, but since you have two cards for four display, you should be able to use them.
I'm not sure if both HDMI TVs can use the same card, or if you use one on each.
I was hoping you might reply to my post, I just wasn't sure that I should have hoped you'd reply on Christmas Day. :-)
Have you had much experience with the Moshi product? It seems to have gotten horrid reviews. I'm looking at a similiar option from Cables2Go, but it's basically the same adapter.
Yes, I thought I'd go with the dual cards, since I needed at least 4 displays and I'd split it 2 to each card. That's good news!
A friend has used the Moshi adapter woth no problems, but some reviww do say it is delicate.
Maybe the Belkin cable is more rugged. It is too new for reviews but Belkin has been making adapters for a long time, so should know what they're doing.
There are other cables with reviews.
It has a useful FAQ sextion.