The EVO 83 is a 2006, isn't it? There was only one year that size was 83. Both the 83 and newer 80 (which is the same 07 and 08 and rather similar 09) will easily handle also powered up 5.3 at your weight when you want some more board power for onshore and stuff. They both do float and ride also in rather decent waves too, but here the 07/08/09 has an edge. Gusty 4.7 is also OK on both boards. Even I have been doing it with my measly 70 kilos. Again though, the more powered up you get and the faster you go, the more the 07 and newer will have an edge.
I don't know exact volumes, but by look and feel, I think there might be 2 or 3 liters in between them. Most is in the rails - the newer boards have thinner rails.
I think you'll be happy with both the 06 and 07/08 as complement to the ET74. If price is a factor, you can safely go with the 83. But when you sail them side by side, I think its rather clear that the 07 is a more refined shape and in the end it will cover more conditions in a composed way than the 83.