If at the catalog schematic of TDA7294 integrated circuit we can add 4 pairs of transistors according to the following electronic schematic, we obtain a high fidelity and power amplifier:
Be aware! The schematic is represented as mono and the PCB as stereo. The PCB schematic does not contain the cooler for the final transistors, nor the one for the power integrated circuit.
Download from here the PCB schematic in Sprint Layout. For visualizing and printing use Sprint Layout Viewer
250_400W TDA7294 Power Amplifier
P.S. Not personally tested. I have designed the pcb for my friend MadMax. This project belongs him. As AndrewT from DiyAudio says, the power rail should be +-55v for 250Watt.