Romex to your amp?

Having replaced some Supra Lorad power cable in my system just recently, I can certainly attest to the significant improvement in SQ that the new cables brought. Still, my friends question seemed to have merit, even though that last six feet of cable made a huge difference in my system. 

I agree that it is not that practical  to run Romex all the way to the amp...and presumably not to code; but the question is whether this set up would compete with mega $$ power cords  SQ wise that are readily available to the hobbyist? 

@delkal. I don’t think many(any?)of us actually have much experience with anything else in our walls. So, the actual SQ is a hard point to debate.

Just to be clear. Everything that skipskip posted above is completely correct and I agree with it 100%. 
My OP was questioning the aspect of whether my friend would have a valid point. 
If we take this scenario one step further, and agree ( or not?) that Romex is the material/cable that is the limiting factor in the power supply SQ to our gear ( particularly our amps) then the question becomes how does a different kind of cable from the wall to the amp ( or other gear) better the sound of the cable in the wall. Maybe the answer is that it doesn't actually better the limitation of the cable in the wall, but that the connectors to our after market cabling are what makes the only real difference....thoughts on this?

@buckhorn_cortez. Not quite right...the zoning departments do have the ability to enforce zoning compliance. This means that if one were to build a structure without the necessary permits --and thereby also not meeting building codes, said department can enforce the removal of the non-permitted construction, if remedy is not made. The option of removal is typically given to the non-permitted building owner...or can be accomplished by the department, if the building owner fails/refuses to comply.

@buckhorn_cortez. I think you should re-read my prior post, you are adding words/points in there that I did not state.
Nonetheless, we are in agreement on the basics.