Will the sound quality deminish over the years?

Thanks Kotta, will do. It's nice to back on a quest for something better. It's what this hobby is all about.
:-)

All the best,
Nonoise

Nonoise - I like how your perspective shifted from the Marantz lacking the highs to it adding mid and bass. The change in perspective caused you to no longer think of it as not sounding as good as the NAD. Now that your assumption has changed for the Marantz, you will likely enjoy it rather than wish it sounded like the NAD. You may still prefer the NAD, but I am fascinated by how our brains work.

I'm not sure about tweeters in my Hyperions HPS-938 but midrange uses ferrofluid for suspension. Ferrofluid dries over time and has to be replaced but I don't know if it is 10-20 or 30-40 years. Also, some speakers have electrolytic caps in xover but it should last perhaps 40 years in room temperature.

As you bring more LPs, more DVDs, more books, more magazines and more of anything with barcodes on them into the house the sound will degrade to the point where it sounds very compressed, very generic and very amusical. Kind of like it sounds right now, most likely, now that I think about it. No offense intended.

Mceljo-good point. My first reaction was something like "who covered my speakers in cheesecloth?", it was that big of a difference. Although I've written off the tuner since I got it for so little, I'm still not used to the trade off in sound. Having a bigger and fuller mid to bass response is nice but it seems to dominate the already limited frequencies in a disproportionate way. I guess one can say it has that classic Marantz house sound from the 70s. I once inserted an old Marantz receiver (I believe it was a 2030) into my system and the sound was very similar: big, full and wooly.

Like Kotta pointed out, different tuners will sound different in the context of any given system, just like any other component.

All the best,
Nonoise