I have an HD560 Ovation II, at that time (early 90s) the top of Senn's dynamic line. Even so, it's competitive now only at about the $80-100 range. The 520 II should fit in somewhere below that, probably at or slightly below the level of the current HD485. I don't know if it makes sense jumping straight to a K701. I'd think in the $120-150 range for a clear improvement, and if you have the money sitting around think of getting a dedicated headphone amp as well, and you could easily make a noticeable upgrade from a stock soundcard as your DAC. Search around this forum to get an idea of what is out there and what might appeal to you. For headphones, you might begin thinking in this realm: HD580, K501, DT880 2003.