This topic has been covered on these forums almost ad nauseam (including at least 1-2 threads within the last 2 weeks). But nevertheless, it thought I'd add my experience.
[And yes I debated strongly whether to put this in an existing thread or make it a new thread. But I decided to make it a new thread. My apologies to those who are sick of this kind of thread]
I own an Oppo 980H. I've been very satisified with it, but nevertheless I got a chance to get a Marantz SA 8001 CD player for a good price about 6 months ago and so I decided to test it. Immediately I thought there was a notable difference. Placement of the orchestra was immediately much sharper, the instruments sounded much closer to their real natures (but by no means perfect). Subtle bits of instrumentation could be heard in what from the Oppo would just be a mass of sound. This made recordings overall much more enjoyable for me to listen to almost from the get-go, and this feeling stayed with me Over several months. I did some comparisons with some recordings I know very well, and enjoyed them much better on the Marantz than on the Oppo. It just sounded much closer to the "real thing" in the Marantz. And to my ears it was not subtle at all, but quite noticable.
Anyway, I recalled all this again today. I just finished listening to a favorite CD of mine (Mario Pollini, Beethoven's Late Piano Sonatas) and was struck again by it. Pollini's piano sounded more like a piano on the Marantz than on the Oppo, and while again no recording is perfect I can hear sublties of the instrument (which frankly would probably only be audible to a pianist or former pianist) with a fidelity lacking in the Oppo. The kicker is in the high notes - this was sometimes a mush on the Oppo, especially when it got loud (e.g. the end of Sonata #31 Op. 110). When I hear this on the Marantz, not only is the mush gone but the notes sound like they actually came from a process closely resembling hitting sevearl keys of a piano. This was not just a comparison of one chord, this was sustained throughout the entire ending of that piece. I noticed and enjoyed it enough to write up this little screed.
All this to me is more than enough. I don't care about double blinds tests, psychology and the like. I hear the difference, and for me it's more than worth it to have the Marantz.
Is my comparison fair? Only partially. I'm using the same equipment, the same (acoustically poor) room. I'm not conducting a double blind test, but the difference is noticable that I believe with high confidence that I would hear it, and that a test is unecessary. The only difference Oppo feeds PCM into my pre/pro via a $150 coax cable, whereas the Marantz feeds into the prepro's analog stereo inputs via a $150 set of interconnects. I recall that the sound from the analog outputs of the Oppo was a bit warmer but I thought more muddled and not as good; some swear that the Oppo is as good as any other player when used as just a thing to send out digital signal. I don't recall the Oppo performing better from its analog outs, and I'm not interested in the subject enough to test the digital outputs of the Marantz. All I know is that the way I have it set up to Marantz is to my mind much better
So, is the Marantz worth more than the Oppo? That's a judgment call. If you couldn't care less about, or couldn't discern, the subtleties I'm talking about above, then I'd say don't waste your money. I also personally think you have to have a strong love for music, and have played an instrument in the past, in order to hear the difference. But if you can discern problems like what I'm talking about with your "lower end gear", then I'd say buy the higher end gear. Just be sure to get a return policy.
And no I don't work for Marantz and I couldn't care less what label's on the gear.
Equipment: Cary Cinema 6 pre/pro, Cambridge 640A 2 channel integrated amp, 2X Monitor Audio Silver 6 speakers, Harmonic Technology Harmony Link interconnects, Stereovox XV2 digital coax cable. Room with bad-to-poor acoustics. (I'm not going to touch the issue of "whether all this gear is better than Radio Shack gear" and "whether the difference I hear between this gear and Radio Shack gear is a a psychological delusion")