Dedicated AC line - Contractor wants to use BX instead of romex

I would not want/use regular AC armor cable, (commonly called BX cable), to feed audio equipment.

If AC must be used spec AC HCF only.

Example of regular and HCF AC cable:
https://www.afcweb.com/cross-reference/comparison-ac-mc-cables/
Look at the diagrams of each shown at the bottom of each.

Example of construction of regular AC cable:
https://www.afcweb.com/ac-hcf-armored-cables/ac-lite-armored-cable/

Example of AC HCF cable:
https://www.afcweb.com/ac-hcf-armored-cables/hcf-90-health-care-facilities-armored-cable/

IF MC (Metal Clad) cable is allowed it is recommended over AC cable for branch circuit wiring to feed audio/video equipment. MC is even recommended over MN (Romex) cable.

AC and MC are not the same.

.

As a result the most likely best path forward is to use the hi purity copper in conduit.

It’s just 10-2 with ground NM (Romex) cable that has been sent out and cryoed.
(Not by the manufacturer).
I wonder what the electrical inspector would say about that?

OP said:

I was planning on using VH audio cryo’d 10-2 Romex

CORRECTION:   

jea48 said:

IF MC (Metal Clad) cable is allowed it is recommended over AC cable for branch circuit wiring to feed audio/video equipment. MC is even recommended over MN (Romex) cable.

That should read.

MC is even recommended over NM (Romex) cable.

WOW I am a recently retired electrician (35 years) and what needs to be said here is we need to be careful of your opinions when you don’t have the knowledge. This could be dangerous to life and property. Sometimes the local codes are contrary to what we want for our high end audio. There are reasons for the local amendments to the NEC and these local amendments must be adhered too. I’m not going to try to educate everyone on this site but some of the answers show a lack of understanding to the trade. This is where the danger is. When we choose to ignore this that is where we get in trouble. 
Always remember the NEC is written to prevent electrical fire which are usually catastrophic. 
I love my audio like we all do but not at the cost of life safety. 
Enjoy safely 

Considering that pretty much every state has as law the National Electrical Code, what place where laws don’t matter do you live? Cities often take these things more seriously because fires don't just take out one house, they can take out a whole bunch.