Martin Logan Quest Z Bass - can it be fixed ?

The only ML's I've liked are the ESL's sans dynamic drivers. As much as I like to listen to them, I couldn't live with them. Please keep in mind, like most panels they can sound very different in different rooms, and they can be quite fussy about set up. Not the easiest or cheapest to amplify properly either.

Did Martin Logan fix what?

It's nice to get advice from people that know more about Martin Logan speakers than Gayle Sanders himself. With all of this advice I am surprised nobody mentioned the OP's choice of amplifier and how his Onkyo M-504 will alter the speaker's sound quality while trying to deal with the Quest Z's wicked impedance curve while it drops to 2 ohms.

Rrog - are you saying the M-504 cannot handle low ohm loads ?
Guess I never really looked that deeply into 'engineering quality' specs.

From AK:
"No problems with low impedance loads. A very fine, dynamic amp."

I tend to think, from what I've read re the 504 over the years, that at my volume levels, it'll have no trouble.

Should I think differently ?

I think IF I get them, maybe I'd try upgrading the x-overs...not sure.

Mikey44, the ML's are bear to drive, puny amps need not apply. These measurements suggest that the specs don't really indicate just how difficult:
http://stereophile.com/content/martinlogan-quest-z-loudspeaker-measurements
My suggestion is to buy amplifiers for speakers, not speakers for amplifiers. Most of the speakers you seem to be considering are not easy loads. Think in terms of total system synergy.