I echo Kchahoc's and Bigbry's advice. Speaker/furniture/room interactions affect soundstage in a big way, as does listening position. You need air behind and around the speakers and you need to sit about as close to them as they are to each other. This is vital.
Drr diamond's recommendation of SACD is probably good if you can find the music you like. Nothing digital beats a good LP for soundstage depth, but anything is better than redbook CD. Even the occasional great CD on a high end system suffers from a certain two dimensional flatness. Your ears are obviously good enough to have noticed, hope your wallet won't mind!
Magnepan speakers and nearfield listening together. I have a 10 X 17' room with the speakers on the long wall. They are slightly less than 4 feet from the wall and my head at listening position is about 68" from the inside edge of the speakers. It projects a surprisingly deep soundstage, sometimes seeming the performers are beyond the back wall.
Magnepan speakers in general are superb for giving a very three-dimensional soundstage, one reason I keep coming back to them. I've owned three different models over the last 27 years.
Is deep soundstage a reality? I go to the symphony a lot and sit 9th row center. I often get a deeper soundstage at home that in reality....and I too like it. And, I use mostly Krell electronics, which don't overly deepen the soundstage.
I recently added SACD capabilities to my system and a few night ago played a Telarc Beethoven's 5th symphony. In SACD, the soundstage was amazingly deep, but when I change to the CD layer it all flattened out.
Wow Jab . . . FMS Cable. That's it nirvana from wire. Didn't ask to see how close to the back and side walls he has his speakers. Or even if the are located far enough apart for where he is sitting. Just great to sell him expensive wire that will do little with his current set-up. Turn him off and lose another customer. No wonder hi-end is dead. Gonglee3, buy a test disk from stereophile and a sound level meter from radioshack. Move your speakers away from the back wall until the best curve is obtained. Then with something like good pop or rock with a singer in the middle move the speakers apart until the center image starts to become diffuse. This will be pretty wide so tow them in if you are sitting close. Make sure that they are even and that both are playing the same level or you need to adjust balance. Listen to your music and then see if your staging is better. And don't think cable will make a bad system sound better. Good cable is for systems that are already hi end. If you are unhappy about wire check out Tara Labs or XLO . . . anything with copper stranded, teflon insulated wire, and good connectors. Happy day, Keith
Pulling the speakers away from the back wall and removing the furniture between the speakers will help a great deal. If you've done stuff like that then it comes down to better equipment and tweeks.