The conditions you sail in sound very similar to mine. I usually float betweeb 80-86kg, sail a Hypersonic (basically same dimesions as an I122), and mainly for the last 10 years have sailed pryde, but have also had some North & Gaastra rigs.
I can't comment on the new North rigs, but I can on the Pryde. I have just got the new RS Racing in sizes 8.4 & 6.7. Last year I had the RS6 in the same sizes. I use the 8.4 on the gusty 10-20 knot days and the 6.7 on the 15-25 knot plus days. The RS6 was a great sail with awesome range, you could really hang on when the gusts were up, and to be fair, there wasn't any other combo's around that were any faster.
You may also want to reconsider your sail size choices, as I have found these 2 sizes to work best over the last 4-5 years and havent had a 7 in my quiver for that time. We have an aweful lot of 10-13 knot days that a 7 just doesnt get you going, and with the range of the 8.4 RS sails, theres no need to rig down.
I have sailed the RS sails with the X6 masts, with no problems, they work great. I now have a X9 boom and consdier that purchase way more effective than a X9 mast, in added performance.
Rotation was the only problem with the RS6, and boy has that been fixed with the RS Racing. I can confirm that the RS Racing has more low end grunt, more top end and rotates like a RAF, no Bull! Even thought the dimensions are the same between the RS6 & RS Racing, the shape when rigged isn't.
I can highly reccomend these sails! Just another comment on the booms, I have found there to be little diffence between the X3 & X6 booms. The X9 has made the power transmit instantly to the board, whereas my old X6 would feel 'spoungy'. I have the 180-230, this covers 3 sail sizes, so it makes good economic sense. I have a small X3 for bump & jump. I would never consider a X9 mast now, unless you are a pro sailor or cashed up!