The B-street is my current go-to board for daily riding and I LOVE it. It's soft enough to be playful, but still stiff enough to handle the whole mountain. There is a pretty big difference between a 141 and a 148 - how much do you weigh? I weigh about 110 pounds and find the 141 to be an ideal length.
As for boots, I too started out with the Casas. They are fine for beginners, but if you have the funds, it will be worth your while to get some nicer boots. In particular, the Casas are very soft and unresponsive. They also cut off the circulation in my feet. I now ride Salomon Ivys (a mid-stiff boot) and am much happier.
As for bindings, the Madisons are solid and are well-suited for all-mountain shredding. I own a pair and my only complaint is that they are a bit big for my tiny feet: I wear a size 4 boot and they are both too wide and a smidge too long. I also own a pair of K2 Virtues, which I love. Very comfortable and comparable flex to the Madisons.
You should also consider Union Trilogy and Ride DVa. I would actually recommend finding new boots first (always try them on before buying!), then try bindings with your new boot to guarantee a good fit.
Yay for new gear! Have fun shopping!