Did whomever advsed you to get 4.5 m2 and 5.5 m2 rigs suggest that you will need close to 20 knots of wind to plane on pretty much any of the GO boards with thse relatively small sail sizes?
It sounds like they may have suggested these sail sizes based on the fact that you still need to learn the basics of windsurfing.
And, since your bride is smaller, it would be good for you to have very lightweight, but powerful rigs to learn on.
Women almost "require" lightweight powerful rigs that can be tuned to reduce power, if they are going to learn quickly and learn to love the sport.
Heavy rigs, or wave/bump and jump/freeride rigs in the 4.5 m2 -5.5 m2 range usually don't have much power and are quite heavy as they are built for wavesailing, bump and jump sailing or very strong (20 knots +) windspeeds.
Since you are small and so is your bride, one of the smaller GO boards would seem the best in the long term, but it won't be the best for you to learn on initially.
Smaller GO boards are less stable, and since you are sailing on freshwater lakes, you get no benefit of the better "float" of these smaller boards when sailed on salt water.
If you haven't already taken some lessons, it might be more cost effective to take a few lesssons to get the basics mastered, then look for a board of your own, as you will be over the first major hurdle in learning to windsurf, and will have the basic skills, balance and technique you need to progress quickly on a smaller more high performance GO board.
As far as which supplier is closest, I'd suggest an email to Tridentsports.com, the US and Canadian Distributor for Starboard.
Here's their link:
Trident Performance Sports
1576 Bay Street
North Vancouver, BC
Hope this helps,