The closest thing to your Studio 40 is the Stage 800. Probably overkill for your needs, but if you like the variety of amp models/cabinets/tones you can get from you current amp, then the Stage 800 is the way to go.
Many people love their Rumble 100s, and if that turns out not to be loud enough, you can daisy chain it with another Rumble 100.
And of course another option is the Rumble 800, which has a low power setting, limiting it to 100W. If you like Rumbles, any of these are great options. You'll just need to decide on your needs and budget.