I really like your conclusion on the double sided magnet HE-400/500 pair, very special headphones both worth owning. Though, never use velours with the OG HE-400, I found the HE-400 only really work well with the stock pleather pads. Vice versa for the HE-500, the pleathers just dont work but the velours work best there. Have yet try the Focuspads either of these but the velpads were a bit too loose for my taste. HE-500 don't shame the bass of the HE-400 in any way either, I actually found it easier to track sub-bass on the HE-400 due to it's less upfront signature and more spacious sound. HE-500 is all about those intimate magical mids that no other headphone can bring, in combination with non strident and smooth highs to me, the bass on the HE-500 can blend sometimes too much into the track as the spaciousness is not really there. HE-400 does this better there imo. Mind you, mine are all unmodded, un-eq'd and run them through a very clinical topping E30 and SMSL-200 combo.