How much power is too much for a Quad 988?

Surprised? Quads are one of the all time great speakers within their limitations. They are tougher than you might think IMO. The protection circuit ought to kick in before damaging them. If you are really worried, bi amp them with a sub and they will play very loudly as it is the bass that will typically cause arcing.

You can overdrive them if you try; I had a customer who regularly did so and damaged them several times. But they were in obivious distress before this happned. The 63s would do about 97db at one meter, I didn't sell the 988s but I believe they will go slightly louder. The size of the amp isn't as important as keeping a reasonable level. As the previous poster said within their limits they are a great speaker. Great for jazz, folk, classical at reasonable volume; not so much for rock. The protection circut is like a parachute, it will probably work but best avoid using it.

I will give you the standard power amp answer. Its always better to deliver clean unclipped power than distorted power. The Quads I understand can take only so much before frying but you listen at low levels. If you want to follow Stanwal's advice get an SPL meter and stay below 90-95db. That is pretty loud actually so it is unlikely that you will approach that and you don't need to buy a new amp. Of course it's a good excuse to get that amp you have been lusting for.

Gentlemen ,

Your replies and counsel have encouraged me and I have downloaded a free Iphone SPL meter program and will self police myself and keep things at 89 db or less.
I was kind of hoping someone would encourage (enable) me to shop for a new Quad friendly amp, LOL

I guess I am more neurotic than I first thought. Keep the advice and tips coming. I don't listen to too much rock, maybe the occasional 70's British "Prog " stuff like Gentle Giant but again at more apartment like levels.
These speakers may help me save my hearing from further damage, who knows? Thanks again to all who offered their 2 cents and more.I really do appreciate it. Now what kind of subs do I need? hmmmmmm?

Open the bottom and check the flimsy sand resistor in series with the input, being paralleled by a 220uF lytic.

These are the things that would break over time and cause the speakers to distort prematurely, with a domino effect of getting the triac clamp that is activated by ionization detection to kick in and shut down the speakers.

This is a protection mechanism that is very hard on solid state amps so user-beware.

There's another thing called a thermister next to the resistor and cap that supposedly increases in resistance when the speaker is overdriven. But that thing does more harm than good IMO.

Check out other 988 989 postings on the forums on how to upgrade and watch for failure.