Lepai LP-2020A+ Class-T Audio Mini Amp $19.49 + FSSS
Amazon Marketplace has it for $19.49 + FSSS , or get it from Amazon itself for a couple dollars more.
• Power output: 2 x 20 watts RMS
• Input impedance: 47k ohms
• Frequency response: 20 Hz - 20 kHz
• Input sensitivity: 200 mV
• Minimum THD: <0.05%
• Dimensions (D x W x H): 120 x 147 x 42 mm.
CNET has a good review of the LP-2020A+. An excerpt:
The amplifier's TA2020 amp chip incorporates Tripath's proprietary Class-T Digital Power Processing technology. This chip was cited by the engineering magazine IEEE Spectrum as one of the chips that "shook the world" when it was introduced in 1998. No wonder Tripath amplifiers have earned a reputation for sound quality from budget-minded audiophiles, and the LP-2020A+'s rich tonal balance won't tarnish that impression.