Am I overpowering my drivers when they

Budding enthusiast here trying to figure out why the drivers in my speakers "pop" at medium-high volumes. I've recently decided to explore the world of "new vintage" speakers and amps (70's and 80's era stuff) in 2 channel for listening to music after a few years of 5 channel supported by a Harmon Kardon AVR 320, Axiom M3Ti mains, Axiom 150 center, Wharfdale surrounds, and an Acoustic Research 12" Sub. This setup just didn't have the presence and power for music that I felt I could get with bigger drivers/enclosures. The little Axiom's are impressive speakers with wonderful detail and clarity, but their small drivers/enclosure limit their capabilities. So I hit Craig's list and started my quest to put together an inexpensive yet repectable system using proven and repectable older gear. First I acquired a Carver 1090 integrated amp to power my 2 channel system and have been picking up speakers as I find something interesting and inexpensive. So far the collection includes Pardigm 5SE's, Polk Monitor 10A's, and Cerwin Vega VS120's. I'm also using an Onkyo 7-band EQ and usually have the loudness activated on the Carver. Problem is, at volumes that are just starting to approach "loud" (output on the Carver showing about 40-60 watts and volume knob at about 30%)...and by "loud" I mean you could still carry on a conversation without yelling, but you'd have to speak loudly...the drivers on the Polks (two 6.5" drivers/speaker and a 10" PR) and the Paradigms (one 8" driver/speaker) start to "pop", like they are being pushed too hard. Maybe my expectations are set a little too high, but I thought either of these speakers, with a clean amp like the Carver (it is a clean amp, right?), could get pushed pretty hard before the drivers started to make that "pop" noise that I always associated with a driver that is being driven too hard. The bass level knob is dead in the middle (would that be "flat"?) on the Carver and the two lowest frequencies on the EQ are just a little above the half-way mark (zero). The Carver has a little needle that shows db output, and I think I'm seeing about -20 or so when the drivers start to pop. Both speakers have rubber surrounds on the drivers and they all look good. At medium volumes I'm very impressed with both the Polks and the Paradigms, but I was hoping I could get a little more out of 'em before they started to lose composure. Could there be something wrong with the amp?
What music are you playing and by what bands? Has the bass in the music been anded to? Is it on more than 1 piece of music? Are the speakers ported?
Wouldn't the "started to lose composure" be the early sign of the amp starting to clip;thats what I would suspect.
I agree with playing the system flat and removing the EQ as this elimates a electronic suspect and removes boost to certain frequencies.
Stevecham makes a great point. When I first got the audio bug, or better yet, the equipment bug, I had a Sony integrated amp at 110w a side driving Cerwin Vega D-5's at crazy volumes with the bass/treble turned up. I then upgraded to a Denon PRA-1500 pre amp and Sony TA-N 55ES power amp and used the tone bypass button. It took a little while for my ears to adjust to just how it was supposed to sound without all the added bass and treble I was adding, but once it did, I had a new appreciation for a flat output. Give it a try for a week or so. You will then be able to better hear differences among other pieces of gear!!