Yping - I think you'll find the 20's will continue to get better over a few months of playing
Mine have been in the system for just over 7 months and I still find subtle improvements about every week.
As for your system sounding better than more expensive systems - some people might think you are overstating the benefits of these cables and that it is not possible to attain such dramatic improvements from mere "wire" - but as you pointed out, the reviews all state similar benefits and cover systems of many price points - so can we all be "selling land in Florida" ?
Components today contain excellent "parts", but often certain price point decisions leads to poor design choices that degrade their actual capabilities. What the gZero and zFLOW product range does is provide some "relief" to the effects of those design choices, which in turn allows the component to operate with more precision - allowing for a much improved performance.
One such issue effects the neutral side of a components circuitry. Having any "noise" on the neutral side of the circuit degrades overall performance. The gZero and zFLOW range of products assist in minimizing that noise resulting in the improvements, especially clarity, observed by most owners.
But, they also provide similar benefits to the more expensive product lines, because they also assist in mitigating much more subtle issues, especially those that pertain to extremely fine micro details that those products are capable of resolving.
One question - have you tried your cables on your friends more expensive systems? If so, what were the results.
Regards...