Given that you're playing clarinet in a quartet I cannot help but wonder if you really need a more open clarinet mouthpiece. If I was in your position I would do the following: 1.) Change the Rovner ligature for one that doesn't dampen your sound. It's been my experience that Rovner ligatures do that. I've tried a lot of ligatures over the years and the one that gives me the best results in quality of sound, response, and projection is the Vandoren Klassik string ligature. I'd suggest that you try that first and see what it does for you. Then.... 2.) You might be able to get a stronger sound on your B40 mouthpiece with a thick cut (ie, more "wood" in the heart) reed that is made from higher quality cane. The Gonzalas F.O.F. is a great reed. It's worth a try. I'm thinking that trying these two things first may give you better results with your current mouthpiece.
If you continue to be unhappy with the B40, then you will need to try a selection of mouthpieces to see if you find one that you really like.
Personally, I am very impressed with Walter Grabner's clarinet mouthpieces. They have made a big difference for me on clarinet and bass clarinet. I've found the Grabner K14 to be a fantastic mouthpiece. It has a dark, warm, big sound that rings and has superb projection. The tip opening is only about 1.07 mm; yet, I have no problem being heard in a big band.