My take is that amp quality makes a difference, an audible difference, for the upper end where the low and high mid range reside (the 2" compression driver and the 12" lower midrange cone driver), again, in my opinion amp quality is not audible at the low end.
One thing that I learned with my DIY 4350 is that for the best balanced sound I would recommend identical amps for both low and high ends, initially I had a 100W amp for the high and 200W for the low, when I change them both to 200W I could hear a marked improvement in the overall sound.
Since 4350's are bi-amplified, just turn off the amp that drives the high end and listen only to the sound of low end, at below 250Hz what is coming out of the speaker will instantly prove my point.