Currently, My 60" plasma is sitting on the tv rack and I am planning to keep it on top of the Horizon. I remember reading Dave's post where he mentioned that it can support about 100 lb.
I haven't thought about investing some more money on wall mounting my TV.
The reason, why i am more inclined on towers (than the Sierra) is the reason that i can live without a sub woofer for time.
Aravind