I have used both Nordost Flatline gold and Atlas biwire, and they are both great cables.
The flatline biwire version was originally fitted to my hifi #2 years ago, I had 2x7m runs fitted to the biwire EPOS ES14s and it cost me £250 at the time (mid 90s). The sound improvement over what I had before was very noticable, even the Mrs could hear the difference. Greater dynamic range, more detailed...heard things in the mix that I just hadn't noticed before. I then transferred this cable to my ES30s for some years, by cutting each length in half and using one length shotgunned to the woofer. Then replaced this with twin runs of Townshend ISOLDA (£800).
The ES14s now have 2m lengths of Atlas Biwire, again nice detail and punch, perhaps better bass extension that the flatline. However the speakers are well into the corner of the room so its hard to tell.
I recently tried flatline back on the ES30s so do an A-B comparison with the ISOLDA...there was a difference but it wasn't night and day.
If anyone is interested, I have 4x 3.5m lengths of flatline biwire unused, I think its all terminated (one pair biwire, other pair shotgun) with 4mm plugs all round.