I agree with looking at Top Tube and Head Tube numbers. I have a Giant FCR flat bar that fits larger than an old 1973 Schwinn. From a strict numbers perspective the Schwinn is 66 cm and the Giant is 58 cm but the Giant has a 240 cm head tube which is far bigger than the Schwinn and the top tube between the two is the same.

Overall, I have found Kona to have very large frame options. If you really look at a Dew, I am sure you would find that the head tube and top tube would be bigger than what you have now even if it only says 61 cm. For the record, I am 6'5" and have a 62 cm Jake the Snake and a 58 cm (XL) Giant FCR as my primary commuters and for whatever reason, the Kona feels smaller than the Giant