Reasons to go for the K: in your first post you mention bump/jump and you already know that ride from your K86, so it would be more of the same in a smaller package.
On the other hand, if you want to ride waves frontside in onshore conditions (not just blast, jump and gybe), I suppose a Quad is the ticket (not that I would know anything about it ;-)
I would disagree a bit with Ola about board size/range IF you go for a Kode: yes a K80 would be more alrounder at your weight, no question about that. But there are a couple of reasons to go smaller IMHO:
-You already have a very wide range board that's K86
-You will lose some higher wind range with a K80 compared to K74. Yes you'll have more range overall (low+high) but also a big overlap with 86.
-From what you wrote I understand you have solid reliable coastal conditions (which is not my case) so you will start to use 74 in less average than 30
-Even with a 74, I think there is still useful overlap with a K86, it's not like you have a "hole" in covering all conditions: depending on conditions you can safely use sails from 4.5 to 5.0 on both boards.