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.