Speaker Cable Gurus - Need Recommendation

I have moved my NHT 2.9 speakers (driven by CJ 2250 SS amp via an AES AE-3 pre), and need longer speaker cables. Since the cables cross a fireplace they need to be flat (or very, very close), easy to manipulate, and preferably clear or white. 12 footers needed. Cost IS an object, since $400 is probaly my limit (for now). I listen mostly to classical (orchestral & chamber) and jazz (both acoustic and electronic), but rarely at earth shaking volume, and prefer something that does not limit frequency extension at either end. Am aware of Nordost Flatline/Blue Heaven, but welcome opinions on those vs others. Can you guys help with some more cable recommendations, please?!?

Thanks!!