Bass leaves after amp warms up?

Yes, maybe someone reading this in NYC area can help. If dealer is not local, it's hard to audition, for sure.

At this point, I just think the over-driven amp theory has the most evidence communicated to support it. Find one that will not break a sweat into 4 ohms or less and has plenty of gas to spare as a reference for comparison. That means on paper its specs indicate double the power into 4 ohms as eight. Its the only way to know for sure.

If there are any online sellers or vendors that offer money back satisfaction on amps that might be tried, that would provide a worthwhile option to pursue with little risk, other than shipping costs maybe. A good Class D amp might fit the bill and be practical to try due to small package and lighter weight for shipping.

A respected dealer suggested I purchase a sound level meter.
Measure a bass test one when it sounds good then again when it changed
Does this route have potential to lend "credibilty" to my claims
AP

Not only credibility, which isn't too important unless you are running for some type of award, but more importantly it might lead to a solution.

I have not read all of the posts. This has probably been addressed, but I'll risk it. When using a SPL meter as a guide once your system has 'warmed up' you just might find that by moving the listening chair (I assume you do all your critical listening from a centered seat in a close to equalateral triange) backward or forward (as little as 6" can may a huge difference in the bass) or the speakers but not so much, and take advantage of nulls or nodes caused by your room and or speaker/listening chair placement.

Just a WAG, but judging from your system photos you might yet have something to learn about set up and room acoustics. Just a guess mind you.

If you need help learning how to use a SPL meter just ask.

Good luck.

I wish to retract what I said earlier about PSB support
I spoke to a representive at length today
He was patient+responsive but feels it's an acousticial issue

Fishing, Al (Almarg) and Ralph (Atmasphere). I just read above that there is speculation about the ability of the variosu amps used to drive low impedance speakers. Dunno for sure.

But if that is the culpret, then I see 3 options: (1) change the speakers; (2) change the amp; or (3) Zero Autofomers. Not sure what the least expensive route to take is.

As regards option #3, check the web site. I think the guy who came up with the idea will take the Zeros back if they don't work. I think #3 is about $1,000. Bummer.