If I remember correctly, each amp module is limited to 15A by design. The protection that holds it still at 15A even if the demand is higher is what makes the amp unclippable. Beyond that, you might need different fuses to really get more from a 20A (additional 5A for the 7 remaining channels).
From the "reliable source", it was never entirely clear wheater the amp is just "capable" of handling 20A (but not shipped as such) or if its main fuses are already able to draw 20A out of the box.
Its the latter from what I understand.
Also there is another significant difference between the 2 amps besides the number of channels and price . The A-1400-2 amp has the benefit of those huge 140,000mf capacitors for just 2 channels as compared to spreading them over 8 channels. That's a heck of alot of power on reserve which is why my amp keeps playing for up to a minute after I shut the power switch.
