What are the rules of the project?
Did your teacher say, build a transistor amplifier with any transistor you like? If so try an LM3886 transistor. Parts required 9. You will need a heat sink and a DC power supply. This audio transistor puts out 68 watts. 28 volts = 38 watts to an 8 ohm speaker. 35 volts = 50 watts to an 8 ohm speaker. 94 volts max. If you do a web search for LM3886 circuit you will find several.
Look at how small it is. **broken link removed**
Or is this a project where your required to look the transistor specs up in a book and design your own circuit that works?