Power conditioner wire gauge? Serious issue

FEW people recommend 10 gauge wire from the panel.  Depends on the distance.

The main issue is resistance (R) per foot.  Here's the difference, per foot, at 72 degrees:

10:  0.00102 Ohms / foot

12: 0.00162 Ohms / foot

14:  0.00258 Ohms / foot

So running a 30' 10 gauge wire would be:

30 x 2 x 0.00102 = 0.0612 Ohms

Now, for the 6' of 12 gauge you want to run between the wall and your amp:

6 x 2 x 0.00162 =  0.0194

So the 6' of power cord is 1/3rd of the entire resistance. 

PS - We use 2x the distance because both the hot and neutral count.

OP: I think you need to stop thinking of 10 gauge as some magical ideal. It is not. It’s just better by immeasurably small amounts per foot and most 120V outlets will accept it. 

At 10 Amps of draw, the hypothetical 30’ 10 gauge wire would drop 0.6V vs. the 0.2V of the 6’ power cord. Tiny amounts relative to 120V incoming AC.

To answer your question, you will have no problem using smaller gauge with your 10 gauge wiring, don't worry about it.