Will the sound quality deminish over the years?

Chance are that your own earring will degrade as fast as the loudspeakers themselves especially if you are over forty .............

I think Rocc1007 says that in jest.

Recently I had to replace my NAD 4300 tuner as it just stopped working (after a couple of decades) and replaced it with a Marantz ST-6000 which has all the bells and whistles one could hope for (presets, remote, great selectivity) and a very positive opinion from fmtunerinfo.com. Having said that, it's frequency range is 20Hz to 15KHz and these 60 year old ears can most definitely hear the upper end roll off and it was offputting at first, to say the least.

I got it for a great price being an old demo but I'm still looking for another tuner that can at least replicate the sound of that old NAD. I really miss the air, ambience, sparkle and whatever else lurks up there in that other 5KHz that was left out in the design of the Marantz.

As for your question, the surrounds of the speakers won't be up to par so if it at least looks to be in decent shape, I wouldn't push it with the SPLs. :-)

All the best,
Nonoise

Hate to be a buzzkill...but FM frequency cuts out @ 15 kHz...so the improvements attributed to the Nad are largely imaginative...that said, its a very good tuner.