This question is like "How can I make my bicycle accelerate like a motorcycle?" Honestly, it's asinine to expect headphones to have the same presentation of speakers. First there's a recording issue, that most recordings have speakers in mind, and when played through headphones, you won't get that frontal soundstage. You could try looking for rare biaural recordings are tailor made for headphone listening. When soundstage is discussed on this forum, it's very subtle compared to even the headphone with the widest soundstage. The AKG K1000 has the widest soundstage of headphones, and its design has it working like speakers placed far away from your ears. I've never heard it before, but I doubt it can compare to what you get from speakers, and definitely not that frontal soundstage since the position is still next to your ears. I have the arguably the next largest soundstage headphones in the HD800, and I can tell you it's nothing like speaker presentation in any way. All it does over smaller soundstaged headphones is a sense of more depth and air on either side of your head, and even then the difference in perception might be a foot away vs coming from inside your head. I don't know about software on creating a frontal soundstage, but I doubt its results will be what a real speaker sounds like, or it would be more popular on here.
With all that said, your HD600 is known to have a shallow soundstage relatively, and if soundstage is big for you, a different pair of headphones would be the way to go than trying to suck out the last drops of soundstaging of your HD600 through various amping. Remember though, even then it would not be anything close to speakers.