I am assuming that you are looking at a used C5, as the price wise c5 must fall into an upper category. I had a FiiO e12, and now a c5d. After longer use, the analogue FiiO control has slight scratching noises when turned, also channel imbalances before 9 o clock. I dont know about a3. Seeing your signature, if your really like your Beoplay to be neutral sounding, go for the JDS. E12 was fun, but not neutral. Exaggerated mids are good with voices, but C5 always brings that sparkling nuances in the upper frequencies which the H6 are good at. Bass wise, FiiO adds lot of body, JDS sounds thin. BUT; JDS is tight, decays are fast, and its a much more dynamic listen than FiiO. I am ASSUMING FiiO A3 to be inferior to e12, as I had only e12. May be A5 will be a good competitor. If you know any place where you can buy c5 for the price of A3, do let me know too..
One thing annoying about JDS is the battery life is compartively lower to fiio products.