Here is a great example of a DIY amp project. The TDA2050 Hi-Fi Chip Amplifier looks like a good chip to use for this purpose. There is full schematics and details provided so that you can build your own.

Thanks Gio.

"The amplifier is built around a single integrated circuit (IC), the TDA2050V which is produced by STMicroelectronics. From the data sheet, the TDA2050V is intended for use as a Class-AB hi-fi audio amplifier. The chip will operate within a supply voltage range of +/-4.5V to +/-25V. At about 25W of power output the efficiency is about 65%. One thing to note is that the gain of the circuit needs to be at least 24dB to maintain stability."