Well of course you CAN buy local... but there's usually better offerings than Alpine... Focal, Hertz, Rainbow, Zapco, CDT, etc, etc, and everything down to Alpine, RF, and and all that... Of course you will save money by buying online, as well as gaining some valuable knowledge if you read around.
BTW, 4x4fun... WTH are you trying to say? Think out your posts for a min maybe before writing... some of it is fine and alot of it is gibberish. By 400 true watts do you mean the added RMS ratings of all four speakers? Also that doesn't mean thats what they're getting, only what you should be giving them. Components don't "suck" power, they are fed it from an amp. No more or less than is given to them. Therefore, a sub doesn't "suck" anymore power from an amp than a component set does, it just in general is able to handle more power.