RE: isonic 122 or isonic 133?
Both boards will adequately cover the sail range for your rider weight. Can you say is the main focus for this new iS going to new more 7.8m conditions (iS122..) or more 9.2m (iS133) ??
Also the size (bigger sail range??) of your smaller board ?? The relationship (crossover) to the new iS could be an advantage one way or the other - for example, the iS122 can be pushed relatively hi up the slalom wind range, especially if you are a "power" sailor. This may be an advantage to the iS122 on one hand, or possibly no real gain if you've got that area (around 7m) really fully covered with your smaller board - and in that case the better choice could be to concentrate the range of the new board on solidly covering (iS133) the lighter end of the 7.8/9.2m wind range (ignoring the "hi wind" potential for the iS122 ).
Let us know if you've more questions or would like more info.
Cheers ~ Ian