Vasia,
I wouldn't think you'd have a problem with adding an additional 20lbs to the top of your tv set. The only concern I would have is if your stand can support the extra weight. Another thing to be cognisant of is the potential for interference with your picture tube. I personally had some problems placing my vp150 atop my tv, though many others have done the same without any concerns. It's just something you should be aware of as a potential problem.

good luck
Scott

"Chickens don't clap."