Trip,
I had BK amp 7250 and I don't think it is right at all it rather warm and tube sound like, so I don't think it is the amp that causing you the bright sound. Monitor 5 is a bright speaker sound because of the tweeter but it is fine with bk I heard it at the store about a year ago. The problem with your system is the monster cable and the interconnect if you can find transparent cable give it a try both speaker cable and interconnect and you go from there. Let us know hope that help.
I had BK amp 7250 and I don't think it is right at all it rather warm and tube sound like, so I don't think it is the amp that causing you the bright sound. Monitor 5 is a bright speaker sound because of the tweeter but it is fine with bk I heard it at the store about a year ago. The problem with your system is the monster cable and the interconnect if you can find transparent cable give it a try both speaker cable and interconnect and you go from there. Let us know hope that help.