Roger offers good advice.
There is never one correct answer because ones progression in windsurfing depends on many variables. Things like - typical winds, number of days sailing per year, plus dedication and commitment to mastering the sport. 95% of us never "master" the sport, but we become hooked on the enjoyment and excitement of the sport.
So, look at yourself and project where you think you want to be in a year or two. Basically, a board in the 110-115 range as Roger suggests is a good recommendation if you "know this is your sport". If you are content with just enjoying the outdoors and cruising around with little stress, the the bigger boards may be a better option.
The smaller boards take a higher level of commitment to master, but the payoff can be much greater. Many of us that have a couple of decades under our belts, usually have between two and four boards so we can maximize our time on the water in any conditions. Where you live also plays a huge role in what gear you have because of the winds and venues. Boston means a shorter sailing season so it's hard to accumulate a lot of days. I don't know about the winds there, but that's where it may be to your advantage to check out what the other Boston windsurfers are using most of the time. Keep it up and you will be hooked. Careful it doesn't mess up your family life.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.