I was told that as we all use optical cable to DVD player, there are not too much difference between top or cheaper DVD player, as long as you have a good quality reciever/amp to manage the data from optical cable?
Not true, a top of the line player will be considerably better than a cheapo. How much difference you're going to hear depends on you're ears and audio equipment.
I got Marantz 7600 reciever, JBL L890 4way speakers, what kind of DVD player do you think can match well to it? Marantz DV-7600, Denon DVD-2910, DVD-3910? or others?
I'm not an audiophile, I don't know the best players for audio. If you're really interested in audio quality, post something in the home theater section, surround sound or home theater setup & planning maybe. The audiophiles hang out more in home theater than home video.
The 3910 (which I have) has been replaced by the 3930, which soundwise and picturewise should be (according to tests and reviews) another significent improvement over its predessor. I have not heard/seen the Marantz 7600, but have read many good reviews. The 2910 is now the 2930 which is also an improvement I believe. If money wasn't the issue I take the 3930, but sound quality is really up to your ears as we all hear a little differently and have different tastes.
Although synergy might suggest marrying your receiver with the 7600.