As one of its Black Friday ad deals, Best Buy offers the MartinLogan Dynamo 10" 600W Subwoofer for $399.98 with free shipping. (Crutchfield charges the same.) That's $300 off list and $49 less than other retailers. Deal ends November 11. Features:

down-firing design

300-watt continuous power amplifier (600-watt peak)

24Hz to 200Hz frequency response

20,000 ohms impedance

rear-mounted 3-position phase switch