This line of Kemo self-contained amps includes low to medium wattage mono amps, and this stereo model. It doesn't get any easier with line level inputs, power, and speaker out leads from a sealed box. Thought it might fit someone's need.
If you can solder , I recommend this http://www.jdslabs.com/item.php?fetchitem=v203PCBG
or if you want something a bit bigger then check www.diyaudio.com group buys, massive bargains and excellent amps. If you can solder they will supply a kit that will cost say £40 and sound like a £300 amp.. its true we are ripped off so much by retailers.