Spkr, interconects, or power cable upgrade first?

Power cables will make the most difference. I would then replace the speaker cables with solid core cables - I'm not a fan of multi-stranded wires.

Regards,

Replace your power cables first, you may not need to replace anything else.

Seems like mixed opinions so far. I can only cite my experience which was: replaced speaker cables first, then interconnects and finally power cables. I too was using Monster cables for speakers. They'd developed quite a bit of oxidation over many years. Went with JPS Labs for all cables (speakers and inteconnects). Some purchased used. Built a DIY power cord for my CD player (go on-line to Parts Express for instructions). Bought a MyAudioCable (MAC) powercord for my integrated amp. Along the pricing continuum for this stuff all the above are definitely to the lower cost end but good value options - at least in my opinion. For me changing out the speaker cables made the biggest improvement.

power cords first..
Larry

As I agree with Ghosthouse that upgrading speaker cables first is the way to go, you have an even three-way split so far. And like Metrella I also prefer solid core speaker cables; they are the only type of cables that I hear a distinct improvement with.
Concerning PCs, they are last on my list. All of my equipment is plugged in via upgraded PCs from various makers and if they make a difference it is subtle (please don't take my Audiophile club membership card away).