Improving 2- Channel Soundstage

I don't know if I'm asking my question in the right topic area but I figured folks with HT experience may be able to help. It may also sound like an odd/stupid question so please bear with me. I'm a 2-channel/stereo audio guy and I'm trying to improve the soundstage in my listening experience. Has anyone tried a set up where you put another pair of (smaller) speakers between the (front) 2-channel speakers, closer together and pushed further back behind the two main speakers, sort of like deeper into the soundstage. I suppose using a "center" speaker/channel is another option. Now, would using the main speakers as front and the two behind them as rear/surround or cenetr speakers and apply an EQ such as "Hall" or "Concert" help with creating a deeper soundstage? This is of course assuming the source material is just 2-channel audio and the EQ choices are based on what the HT receiver can offer. Thanks.