well the firefish wont be of concern but the diamond might be only because he will be sharing the same territories as the jawfish. Most reports I have seen will either be the diamond getting aggressive toward the jawfish, or even the goby just moving into the jawfishes burrow. The jawfish then moves and digs another burrow only to have the goby come take over that one, the chain continues until the jawfish gets stressed out enough and dies.
Not to say that they couldnt get along just fine, but think it might be about a 50/50 shot, with chances improving for larger tanks