The about 660-mW output can be gotten with the 16-ohm speaker.
http://www.interq.or.jp/japan/se-inoue/e_ckt3.htm
This is a three-stage amplifier. Its last stage is a common-collector amplifier, with low voltage gain, high input resistance and low output resistance.
http://www.electronics.50g.com/camp4.htm
Short circuit protected using The TDA2009, A is class AB dual Hi-Fi Audio power amplifier assembled in Multiwatt package.
http://www.st.com/stonline/products/literature/ds/1457.pdf
Using the TDA2030, intended for use as a low frequency class AB amplifier. The guaranteed output power is 12W on a 4W load.
http://www.st.com/stonline/products/literature/ds/1458.pdf
an eight watt amplifier based on the LM383 power audio amplifier ic.
http://www.reconnsworld.com/audio_8wattamp.html
8 Watt Audio Amplifier using TDA2030
http://www.freeinfosociety.com/electronics/schemview.php?id=734
Using LM383. This amp can be used as a simple booster
http://www.aaroncake.net/circuits/amp.htm
10W CAR RADIO AUDIO AMPLIFIER Circuit Diagram
http://www.st.com/stonline/products/literature/ds/1449.htm
Behaves like a one-valve operated amplifier. No cross-over distortion
http://www.redcircuits.com/Page80.htm
3kHz Filter and Audio Ampplifier schematics for optical through the air transmitter.
http://www.freeinfosociety.com/electronics/schematics/audio/3khzfilteraudioamp.pdf