Been mucking around at the yammy dealer's setup. Tried grounding the a-s3000 first, and then the cd-s3000. Both times we noticed audible differences. With just the a-s3000 grounded, soundstaging height increased by nearly a metre, the spaces between sound images cleared up and became less hazy, and consequently, imaging became better delineated, more pin point and more focussed. The soundstage became slightly more recessed further back behind the speaker baffles (if the speakers had been positioned further out from the wall, we are pretty sure the soundstage might recessed in towards the back further more). Overall, there is a weightier foundation to the music and we could listen at much louder volumes than before without getting fatigued.
When we tried grounding the cd-s3000, the effects were the same, but not as pronounced as when the a-s3000 was grounded. However, when we lifted the grounding cable on the cd-s3000 off the carpeted floor, we then heard the same degree of improvements. It seems that the grounding cable we used can be very reactive with the materials that it came into contact with!
The grounding cable we used is a thinny video rca cable (typically came supplied with cheap dvd players) that had been checked for signal flow directionality. The source end was plugged one of the unused rca input terminals of the a-s3000 and the other end was stripped and it's shield was connected to the ground pin of an uk ac plug (with both live and neutral pins removed) and plugged into the wall. When this was done, straight away we noticed that the perennial "buzz" on the front metallic faceplate of the amp was gone. When the ground cable was unplugged, the buzz (which is parasitic electric leakage current) came back. Unplugging the ground, we noticed that the soundstage collasped immediately. I briefly compared the ground cable plugged into Line1 input terminal vs Rec Out terminal, and i thought i can hear some differences, but I'm not 100% sure. It was very subtle.
The ground cable to the cd-s3000 was connected to the coaxial output terminal.
When we grounded the streamer, wxc-50, again we noticed the same improvements.
Cheap tweak that yield very big sonic improvements!
One more thing - after listening to the a-s3000 it was difficult to step down to the a-s2100. The differences are not subtle. If ever I'm in the market for an integrated amp and i have the dough, I'll go straight for the '3000. Forget about value-for-money thingy. Because after hearing both side by side i couldn't be able to live with myself with just the '2100.