The MA6300 is a current model, therefore it is more expensive. I've seen MA6500's between $2,000 and $2,500 in audiogon, ebay and craigslist. A lot of them in like new condition.
About the warranty, the amp is too old so it doesn't apply anymore (even if you never filled the form).
About the warranty, the amp is too old so it doesn't apply anymore (even if you never filled the form).