Was at Symphony on Wednesday and based on a recommendation on this board, my friend and I tried out House of Siam before the show.
It's no Dok Bua, but I was pleasantly surprised. The room is sort of funny -- three levels, quite dark, but nicely decorated. Service was very good -- they were quick and seemingly accustomed to getting people in and out although we never felt rushed. But really what pleased me was the food -- it was cold and drizzly, a perfect day for soup and both the Tom Yum and Tom Kha Gai were delicious. My friend had lemongrass chicken and I had Noodle Kee Mow. I asked for it spicy and it was. Not searingly pet pet but definitely spicy. They have a nice wine list and I had a couple of glasses of the Gewurtztraminer. She had fried ice cream (!) and I tried the taro custard for dessert. Got out of there for $30 a head, which wasn't cheap but was just fine considering the amount of food and drink.
Bottom line: I think this is a good option for a pre-Symphony event meal, a query that comes up a lot. Thank you to the hound who recommended it -- I wish I could remember who it was now.