A deeper more holographic soundstage.

Everything is dependent on everything else. You have been given some very good information on speaker placement, toe-in, room treatments, etc but the truth is some speakers and some electronics do not do a very good job of recreating depth no matter what you do. Generally, tube gear will work better than solid state for depth, but again that's a generalization and some tube gear is better at this than others. Removing componentry from between the speakers may help or may not, depending upon the speakers employed. I have heard speakers produce depth in this configuration and have heard others produce little depth with nothing between them. Experiment with pulling your speakers farther out into the room. You may lose bass reinforcement, but sometimes you have to choose what's more important to you. Good luck and have fun with it.

A good tube preamp will tend to give a much deeper and more room-filling soundstage if the rest of the system is up to it.And yes with a SS power amp.I have heard that effect many times in many systems.Supratek preamps are especially good in that regard and why so many people use them with SS power amps.Especially the DHT ones.Once you hear that there is no going back to flat and congested sounding preamps.

How so and at what cost i.e. what did you give up/lose.

Suspect the OP is thoroughly confused at this point.

I dont have a dog in this fight since I am a home theater buff and dont have a 2 ch setup.

Recently I was speaker shopping at a Best Buy Magnolia and their set up is such that they can switch from amp to amp with a tap of a button. 

I noticed increased sound stage depth and holographics each time we switched from a Marantz SR8015 to a McIntosh MA5300. Like a 20 percent perceived increase of depth.  From that I concluded that sometimes electronics do matter for sound stage even in the solid state category.