Single run of higher quality cable will sound better for the money. Most of the benefits people hear, if any, from bi-wiring disappear when you use proper speaker cable 'jumper cables' from LF-HF on the speaker terminals when single wiring, as opposed to the nasty sounding 'metal links' usually supplied with the speakers. Connector quality will also make a surprisingly big difference IME.
I've gone DSP on my main system, so dispensed with all this, but consequently happen to have some sublime Kimber Select speaker cable, and reference jumpers, I'll be eBaying soon, as I can't justify keeping them for a second system. Not cheap, but they do sound gorgeous (well, to be more accurate, they don't really sound at all, which is kind of the point!).
Bi-amping is a different story, but to do it properly you generally need an active x-over or controller which has this capability. Knowing Meridian there will probably be something in the various ranges which might do this rather well, but others on here would doubtless know better which equipment this might be. But then again, you double your amp cost, add the cost of a x-over, and double your speaker cable cost again.
Makes those DSPs start to look like good value after all
