I don't know the real volume if the 66. I would have guessed 66 was rather close. The 70 is not so much bigger volume vise, but it is a lot wider and this will effectively make it act bigger once moving. The 66 and 70 rocker is rather close (and actually the 75 has a faster rocker) and I would definitely say the 66 is an EVO style board, just unusually narrow. Maybe the reason you felt the 75 was slow was that it was just to much board? That can happen sometimes when you upsize a board for a small person.
I also think part of the fast feel from the E66 comes from the stiffer construction, so that you will have on the E70 too.
In any case, I still don't think the E70 will disappoint you if an upsized 66 is what you want. Since you already had a bigger Acid, I think you can imagine rather well how the Kode feels. Its a similar board, just a bit more refined with both a bit of extra looseness and speed.