I would have to say 2.1.5 L4 or L5, at least for me. But I still switch back to 2.5.1 every now and then. I like them both, but neither is the end-all, be-all because I'm too finicky, lol. To my ears, 2.1.5 L4 sounds more neutral with good dynamics, but the 2.5.1 sounds like it has a bit more mid-range, a sub-bass, and pretty good dynamics, too. I would suggest trying them out and enjoy. I think those two are the best, for me anyway, with my taste and phones.