Those 800W are probably a peak rating. It'll be more like 75-100W at 12V into a single 4ohm load. Alpine's top "1800 watt rated" amp only gives you 350W at 12V into 4 ohms with a decent THD. That 1800W rating is a burst of peak power into one channel only with a speaker coil-horrifying amount of distortion. So don't worry about your alternator just yet... I'd echo Todd's comment about a high quality 100W amp vs. some over-hyped 800W amp.

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon