I have always had fairly good luck with ebay quality . Reguarly buy CD recorders for resale in the store from ebay and so far no problems .

I don't know if the warranty is transferable or not . You may want to check their web page or just call customer service and ask them .

The Pioneer Elite Dv59AVi is similar to the 3910 . It plays both SACD and DVD Audio as well as the usual format suspects . It does incorporate a 4 pin I-link ( IEEE1394 )for SACD and DVD Audio playback . I know this is probably no use to you with the 990 but down the road it maybe useful . I will say that they don't gurantee compatibilty with other brands though . It will up convert to an HD standard regular 480 i signals like the two Denon models . I actually borrowed one of these babys for a few days from the store . Big mistake I must say as I did not want to take it back . The Pioneer has an incredibly sharp picture . Lots of flexibility in the setup menu for audio and pic both .
pioneer link http://www.pioneerelectronics.com/pna/product/album/compare/0,,2076_15020671,00.html

The only real advantage I know of with the 3910 over the 2910 is with the analog processors . The 3910 uses dual Melody hammer head chips while the 2910 has the Melody chip . This gives the 3910 a little more flexibilty in setup, processing power and a wider range of crossover points . The video chips are identical . Both are universal players and have similar inputs and output capabilites .

I can't see spending almost twice the money for the 3910 . I will admit my experience with the Denon models is limited to playing with them in the store . Maybe someone who owns one could give a little better insight . However if you do decide to go with the 3910 you may want to consider the Pioneer which retails for $1599 .