There arent many high end manufacturers that authorize thier products to be sold online. There are a few exceptions made for high volume dealers, but they are only a handful such as crutchfield or sounddomain.

Most products sold on Ebay will not carry the full manufacturer warranty. What do you get with a manufacturer warranty? If it breaks they immediately replace it with another new unit.

Ebay warranty means you send it in and wait for repairs, then it is shipped back to you. The warranty is either offerred by the seller for a limited time 90 days is typical. If its a manufacturer warranty most Ebay sellers let you resolve any issues you have with the manufacturer directly, instead of the seller. Manufacturer warranty personel are very skeptical if you tell them you bought it off Ebay and it broke.

Some manufacturers state in their warranty policy that they will only warranty it if purchased from an authorized dealer with proof of purchase. Also if purchased from an authorized dealer and installed by them you get a full warranty sometimes up to 3 years, if installed on your own its only 1 year.

Its hard to distinguish between refurbished and new stock. Some products are factory refurbished and refinished in a new case, most people would never know.

There are also counterfiet products out there now from Taiwan. I wrote a long article here over a year ago about this new trend. Fake Alpine, Kenwood, Pioneer, MB Quart, Dynaudio, Precision Power, Phoenix Gold were some of the fake products I got to inspect. You cant tell without opening it and looking at the internal parts. Even the factory packaging is official.

Just be careful when buying from Ebay. Im sure there are some good sellers and good products out there. Definitely bargains, but I always remind my customers of the security of purchasing from an authorized dealer.