Mac 6500 w/ MC275?

I own a Mac 6500 integrated and drive Monitor Audio RS6 speakers with Maple Shade silver plated solid core speaker wire.

Q1) The top end is a little bright at times. Would a different type of speaker cable tone down the bite?

Q2)I am seriously into small scale classical, pop vocals and some opera. Thinking of trying the MC275 with the 6500 as a pre? Any thoughts? My listing room is 15x15.

Note: I purchased a Conrad Johnson 60 wpc (model?) tube amp and tried with my 6500....was disappointed with the sound (sold the amp) so I'm hesitant with the 275.
its certainly not the amp. sounds like a speaker placement issue. the 275 is great too, but i don't think you need to switch.
It's the silver cables. Change to a good copper cable.