Mwave offers the MB Quart 12" 600-Watt Car Audio Subwoofer, model no. RLP304, for $46.67 plus $4.99 shipping. That's the lowest total price we could find by $15. It features an injection molded polypropylene cone and frequency response of 25-160 Hz.
Walmart offers the Pioneer Complete Car Audio Package, model no. DXT-X2669UI, for $89 with free shipping. That's $60 under the lowest total price we could find for similar Pioneer items separately elsewhere, although we saw this package for $4 less last week. The single-CD receiver features AM/FM radio, a 12-character LCD display, MP3/WMA playback, USB input, and a detachable faceplate. The set also includes two 6.5" 2-way speakers and two 6" x 9" 3-way speakers.
Walmart offers the XO Vision Automotive Digital Media Receiver (pictured), model no. XD103, bundled with the Boss 6.5" 2-Way Rear Car Speakers, model no. CH6520, and a choice of five pairs of front speakers for $46. Choose in-store pickup to dodge the $4.97 shipping fee. That puts most bundles at the lowest total price we could find by at least $2. The MP3 stereo receiver features 80 watts of maximum power, a USB port, SD card slot, FM tuner with 18 presets, and auxiliary port.
Note that other receiver/speaker bundles are selectable, but will cost more.