The original "Strings" work well.
I was never really happy with Cello Strings interconnects, although I used them for years. About on par with low-priced Cardas or Kimber (similar construction to Cardas - Litz, although they are *not* Cardas wires).
About two years ago I put in Siltech wires (G3); the presentation is smoother and sweeter (nice improvement in massed strings) and yet more detailed. The place to start is from the preamp to the amp.
I haven't tried replacing the CS3 speaker cables -- anybody's mid-to-upper end cables will probably cost at least $15K, once you buy three pairs of them. Of course, you could get north of $50K without breaking a sweat. The sound is quite satisfying as-is, and so I am not motivated to seek other speaker cables. Perhaps it's because the Cello speakers draw so much current.
You can get Fischer plugs from Fischer in Atlanta or from Michael Perry, and Siltech will terminate with the Fischers, if it is physically possible.
For power, I found that power cords weren't all that effective (I use Cardas Golden). Two items *DID* make a very effective improvement:
1) I use two PS Audio Power Plants in the front-end. I daisy-chain a P300 out of a P600, hooking all the digital gear up to the P300 and hooking the preamp up to the P600. This made a huge difference in detail, bass development, and all but banished the electronic haze that comes from digital.
2) I installed dedicated 20A lines to the front-end and a dedicated 30A line to each of the two amps (Perf II's).
Owning Cello front-end equipment is a process of cleaning up what goes in -- the preamp (a Suite) is very neutral and very clean -- and not very romantic. What goes in comes out, for good or ill.