Widening my soundstage

Your equipment is fine, no need to replace anything. The key to obtaining a proper soundstage is to sit in the near field (no further away than the distance between the speakers) and to acoustically treat the floor and wall reflections. With a friend use a mirror to visually see where the first reflection points are and then experiment with different acoustic treatments. A word of caution, I owned a pair of S100 for about 18 months. Overall, I thought they were very good to excellent speakers, but the thing they didn't do very well was soundstage. I suspect the wide speaker baffle may be the culprit. Also, most music does not have the beyond the speaker effect, so make sure what you're using as a reference truly has this property. Good luck!

Agree your speaker cable is in need of replacement. Have no ideas for you, other than to suggest MIT which is just "what I like" but that's in my rig (which stages huge!). Dunno about those Cardas i/c's either, which didn't work well at my house, although others do like them. The other part of my huge staging is due to Synergistic Research Resolution Reference i/c's; used with the Active Shielding power supply the stage is immense. Maybe more $ than you prefer to spend though.

Go to Immediasound.com and read the Audio Physic speaker placement guide. It's a different approach than most others. Also, try the Cardas.com speaker placement, which is opposite of Immedia's approach. If you get the same results, it's your speakers or music your listening to. I used to use Cardas i/c's. They are fine. You should try their speaker cable, you'll be amazed at the step up. Might be best to keep the same brand of ic's and speaker cables, they tend to complitment one another.