Can someone give me some insight.

This is sort of annoying and I need some help here.I have been auditioning different interconnects.MIT,Nordost,Synergistic Research to name a few.I thought I had a winner with Synergistic but what I am finding is when listening I am loosing volume in lead guitars and lead vocals.I have some Monster interconnects that I am trying to replace.If I just use the Monster IC's the voices and lead guitar is strong and open but there is lack of clarity..When I use any of the above mentioned IC's the lead voice and guitar are toned down a few db's and now seem more in the background.
I will admit that with the above mentioned higher end IC's everything is so much nicer.Are the Monster IC's over blowing the top end.I do not understand why this happens.
Last night I had the Nordost Red Dawns from pre to amp and was listing to and watching Roger Waters in the flesh-live.All sounded really good except Roger Waters voice was subdued and when it came time for some lead guitar it was also subdued and more in the background.This was being feed to my pre by hdmi and bitstream.I then changed to Synergistic IC and it was the same.Then the MIT and still the same.Then the Monster and the lead guitar and vocals returned to being upfront and in your face.
Since all the above higher end IC's exhibit this toning down the vocals and lead guitar I am starting to wonder if that is the way it is supposed to be.This also occurs when listening to cd's via analog direct or digital.
My system is Rotel 1069 pre.Rotel 1075 amp,Rotel 1072 cdp and B&W 683 speakers and bluray ps3.
Any thoughts on this would really help me out as I do like a lot of the IC's I have auditioned.Thanks.
Wire is supposed to conduct a signal, and some insulation is a nice feature. End of story. If you're hearing profound differences like the ones you describe merely by switching wires, one (or more) of them is damaged, or unsound design-wise, or something is out of whack in terms of cable routing (past an interference source?) or lack of insulation or damage to the cable or termination itself.

When I switch from a good cheap interconnect to a good expensive one, sometimes I hear a little more of what the source can do, sometimes I don't.

Given how much you're sweating this, I would just go to Radio Shack, buy some $15 gold interconnects, and spend the money you're going to piss away on wire on upgrading area where you will hear a noticeable difference.
It seems to me that the Monster Cable has a more prominent upper midrange than the other cables. That does not mean that it "boosts" that range; it means that the Monster Cable is rolling off the rest of the frequency range AS COMPARED to the other cables.

What works for you depends on the characteristics of your system and your particular taste, so it could well be the case that the Monster Cable works best for you. Also, most choices do involve tradeoffs, so it is not likely that there is yet another cable that will be better in ALL respects, particularly where frequency balance is the subject characteristic.

You also need to consider that you are used to the Monster Cable's frequency balance so that is your current baseline. You may need to give the other cables more time so that you can become more comfortable with their sound. Once you become more at ease with their sound, you will be more likely to discover their other charms.
I use a good deal of Red Dawn and can tell you, BREAK IT IN...takes a good week of running a signal through it! will balance much better after break in.