I have spent the last few days with the A-21 I got from Bill. Thanks Bill. It sounds really good. Very revealing but not harsh or edgy. If I use the pc as a source playing flac via spdif into the dac it shows why I use a sd card player as my main source now. The sd card player is so much better. Smoother, detailed and silent in operation. Zero back round noise unlike the pc. This amp really lets the SDA 2.3s shine. I don't regret this purchase in any way. I have to make new legs for the rack so the amp will fit under it. It's 1/4" too wide! Oh well, the legs needed to be replaced anyway. I changed the shelf height a while ago and reused the legs and they were ugly. I got some 8/4 jatoba that should look nice. I hope to have them done today.