does high end system need expensive speaker cable

Red Dawn can be a bit bright, so in your case if a less expensive wire solves that problem, it would be an improvement. All copper wire does most things well. Your system has enough high resolution componets, silver or silver plated cables would in most cases spoil the balance.

McIntosh is probably not the firm to place your cable faith in if you're of a more high-end philosophy yourself. I believe they are of what you might call the Rolls Royce school: 'sufficient' cabling is enough, and further comparitive listening ought not be required - a fairly dated viewpoint. On the other hand, there is no disputing that top cable wares can be priced well into the ridiculous zone for what goes into them, and maybe even for whatever audible benefits they may bring.

I don't have experience with your particular speaker cables, but do feel that for a highly resolving, powerful, and wideband system such as yours, it could make sonic sense to audition some options further up the food chain. Does this always mean much more expensive, or even more expensive at all? That is the way things trend in this hobby, though for my own cables I feel I'm getting away nicely with using the very reasonable Acoustic Zen Satoris. Then again, my system is a few notches down from yours all the way around. But I do know that speaker cable can make just as much, sometimes more, of a difference as can interconnect, and that's based on experience.

So I guess my answer is that if I were you, I'd probably feel less than totally comfortable if I didn't at least try out something intended more for your calibre of rig. Not that I'll ever pursue that grade (or expense) of rig myself, but if I did, I wouldn't see the sense in leaving open the possibility that I might be cheaping-out anywhere in the chain - otherwise, what's the point of going for it at all?

Speaker cables are no less important than interconnects. Yours are both insufficient. You don't yet really know what your system is capable of.

NO. Expensive doesn't always mean better.