It's rare to find Plinius amps not providing enough power, especially the SA-250. In fact, I'm wondering if the amp is really the problem. You must be pressurizing an awfully big room. Maybe you should double check your power situation (also don't run the amps through a current limiting power conditioner.) I guess speaker cables/power cables could also be investigated too for excessive length, proper gauge and/or incompatibility with the amp.
You also may want to "back door" the problem by trying a preamp with a little more gain than your Classe. It's common to overlook the preamp, but a preamp can affect every area rather significantly.
Nevertheless, if it is the amps, you got a handful of good suggestions. I don't think you could go wrong with the super powered Edge, Halcro and Boulder models. On the less expensive side, the Parasound JC1 and McCormack DNA500 may work well for you. However, when you need that much power, considerations such as size, cost and heat frequently become an issue. If so, you may want to try a high powered digital amp (like Spectron) to alleviate those issues. If you like the sound, you could even get 2 of them and still save money.
You also may want to "back door" the problem by trying a preamp with a little more gain than your Classe. It's common to overlook the preamp, but a preamp can affect every area rather significantly.
Nevertheless, if it is the amps, you got a handful of good suggestions. I don't think you could go wrong with the super powered Edge, Halcro and Boulder models. On the less expensive side, the Parasound JC1 and McCormack DNA500 may work well for you. However, when you need that much power, considerations such as size, cost and heat frequently become an issue. If so, you may want to try a high powered digital amp (like Spectron) to alleviate those issues. If you like the sound, you could even get 2 of them and still save money.