Mark Levinson’s 400 Series single-channel amplifiers are handsome, but at nearly 18 by 20 inches, they are too portly for tight spaces. For audiophiles needing a smaller profile, Levinson (www.madrigal.com) offers two new amplifiers based on the same technology. The No. 431 and No. 432 stereo power amps are rated at 200 watts and 400 watts per channel and consume half the amount of floor space and half the number of AC outlets. Both are fully balanced and are easy to incorporate into multiroom systems. If you prefer multichannel music, a power amplifier (No. 433) with three channels rated at 200 watts is planned for 2003. According to our math, one three-channel amp plus a stereo amp makes five channels—all in only two small black and silver boxes.