If you indeed only want a board that is a little bit bigger, the EVO 70 will not disappoint you. There are small differences between the 66 and 70, but the general feel is still very similar. All boards in the EVO lineup are very refined for 09 but personally I think the E70 is the most refined and "clean" shape of the bunch. An amazing board. At your weigh it handles 5.3 well.
But for most people a quiver of 66+70 is rather tight. There are advantages though. Both boards will work for almost all your sail which means you can tune the feel on a wave by changing board size which is a really effective way of fine tuning things. So again, if you are sure about what you want, the EVO 70 will be a great addition.
But at the same time an EVO 75 will offer a bit more light wind effectiveness. It has a slightly different feel to it and feels loser and easier at slower speeds but does not have the smoothness of the E70 at higher speeds. The 74 (of course) also has a bit more volume which can be a blessing in some situations. And if you will not use it in more wind than underpowered 4.5, the 75 will still be well within its range also for light weights like you and me (I'm 69 too).
Kode/Acid will be very different boards. Faster and with a different turn. They require a better technique to ride waves well, particularly in slow waves. The more onshore it gets, the more you need to work a Kode/Acid for it to go vert well. The up side is great stability at speed, bot on a wave and in a straight line. And they are very easy and natural B&J boards and fantastic for backside riding and jumping on onshore/cross on.
So if you want to complement with a more effective feeling board for light wind but don't need so much wave riding focus a Kode/Acid might be good. I would suggest going for a Kode 80 (or PA80) in that case.
A final option for even more wave riding focused sailing than the EVOs would be an Evil Twin. For max 5.3 the ET 74 will work nice. It has been my most used board this summer and I've done a lot of light wind sailing. The ET80 could be an option if you're doing a lot of float out, ride in type sailing.
Lots of super nice options... You only need to decide what it is that you really want form this bigger board.