We found the the 8001 to be much more noisy on spin up than the 8003. (it must be a quality issue) And in a direct head to head comparison on my friends system the 8001 and the un-broken in 8003 sounded exactly the same when we used good IC's on the 8003. With the cheap IC's that Marantz supplied the bass was slightly muddy.
As far as the Zylon tray, it does look like cheap plastic compared to the tray of the 8001 but who am I to say that it is not less resonant than the tray in the 8001 as Marantz claims. Overall the 8003 looks better than the 8001 and sounds about the same in our AB test.

If your leery about buying the 8003 then go for the SA15, its on sale for about $1300 since the new version is coming out soon.