The A21 is very smooth, with no apparent grain as far as I can tell. "Etched" is not a word I would use to describe it at all. The HCA-3500 from what I understand improoves quite a bit when modded if done correctly. I'd go with the HCA-3500 if you need/want buttloads of power, and the A21 if you want good power with more refinement. I have heard them both. I own the A21.
