I have no experience with the Elco, but have tried the AZ MC2=Zen and the Kimber Illuminations D-60. The Kimber was VERY forward in the midrange and therefore unnatural. It also showed some muddiness, tubbiness and overemphasis in the bass. It did however show an incredible level of high frequency detail, without evidence of brightness. Otherwise, it showed no extremely obvious flaws. Because of its midrange forwardness, I couldn't use it. The AZ is a better cable than the Kimber, in my opinion. Although it also has flaws, they are less extreme than those shown by the D-60. It is detailed, but not as much as the Kimber. There is some upper midrange brightness, but this doesn't show itself all the time. However, on records that are recorded to sound bright, I found the AZ to be a litle edgy. The AZ also sounds a little rolled off at the low and high frequency extremes, particularly at the low end.
I agree with the previous poster that you should audition these cables for yourself. I rented the two cables that I spoke of from the Cable Company (http://www.fatwyre.com). The cost to me to rent these cables was about $30 for both ($15 for the cables) and $15 for the shipping. They got the cables to my home within 2 days. I was very happy overall with their service.
I have heard very good things about the Elco GI-999 Gold from people whose opinion I respect, but I have no personal experience. I believe that the Cable Company has the Elco for rent. You should be able to arrange to get all three of these cables for rental for approximately 14-17 days from them.