Widening my soundstage

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.

Check "phase" (positive to positive & negative to negative) of all interconnects & speaker cables. I've found with own system going back to basics is where problem sometimes lies. Equipment sounds to be better than mine. No problem there. Although you may want to upgrade to "better" speaker cables. Follow manufacturer recommendations and/or plug "speaker placement" into favorite search engine. My favorite is http://members.ams.chello.nl/rabru/speaker.html

What are the demensions of you room, where are your speakers placed, and where do you sit?

First thing I'd do is replace the Monster speaker cable with something of Cardas Golden Cross which is a bit on the pricey side but it'd be well worth it then listen again. I'd bet you're glad you did!