Walmart offers the Britelite iRocker 15" Powered Loud Speaker for $57.99 with free shipping. That's the lowest price we could find by $11, although we saw it for $8 less in our mention from last December. It features:
1,500-watt peak output
15" woofer, 1" active tweeter
3.5mm auxiliary input
SD card slot
Uncle Sam could take a hefty chunk of your retirement income if you botch this.