My JoLida Part2

I'm totally new to the world of 2-channel so please forgive my ignorance.

Since I bought the player I must say that I'm very pleased with the sound. I've been reading through the posts about how members achieve a 3-D sounstage what exactly is that. When I play cd's the music seems to be centered in between my speakers as though my center channel were active but is not. Is this what a 3-D sounstage is and if so how can I get it more centered in my room.

My room is 20x14x9 with me sitting at the oposite end length wise. There is an open area with a landing from the dining room into the living room where the listening is done. If this sounds confusing I live in an apartment that has a sunken living room only two steps down from the dining level. This area is to my right and on my left is windows with curtains with light blocking material behind them.

The open area between dining and living room is 10ft wide. I was planning to install heavy/thick curtains thus enclosing the living room when listening to music or movies. what do you guys think will I get a better soundstage buy enclosing the area. Should I look into room treatments and how can I isolate dead spots within my room.