Use
http://shopping.yahoo.com
Yahoo searches for wholesale online stores and can save you a ton of money.
Here are some price drops that I found (trying to find a lower price for some car audio equipment)
1600-watt Sony XPLOD Class-D amplifier
ESRP: $349.95
Yahoo: $146.99
1500-watt (max) Sony XPLOD 500-watt RMS Subwoofer
ESRP: $279.95
Yahoo: $94.90
5.25" Sony XPLOD 3-way 170-watt speaker
ESRP: $89.95
Yahoo: $49.99
If I were to purchase 1 subwoofer, 1 amplifier, 4 speakers (my car has four 5.25" speakers), I would save
$547.76
Good deal, eh?