Dedicated 20 amp lines/should i use a sub panel

My electrician recommended a subpanel and I'm so glad I went for it. His reason was my main box was a mix of old and new wiring and I was hearing noise thru my existing line to my Hifi rig.

He knew what he was doing since now I have two separate runs with no metal staples used, with two Hubbell receptacles grounded at the subpanel. He also added a second 8' grounding rod.
There is absolute silence thru my speakers now, and I'm using all tubes. I was able to remove one of my power conditioners since the noise floor is so low.

 

I believe we need to hear from some of our more experienced professional electrical experts here on Audiogon (you guys know who you are).
I'd also really be interested in knowing if there is or isn't an advantage to using a sub-panel if there are openings in the main panel?
No offense meant to those that have answered above.
I also use a sub-panel in my systems.

@almarg @jea48 there are othres also...
A little assistance, please?

I will be running 3 lines all identical in length to avoid ground loop hum, my interest is will there be any difference... negative or positive...from running a sub panel as opposed to just using open spots in the 200 amp panel. the closest and farthest line will each power a REL G1 sub and the centre line will power a Synergistic Research powercell 10 UEF, which is where my  tube cd, tube pre and ss amp are plugged into. this is how my system is presently powered just not with dedicated lines.

Thank you, Larry (lak). Jim (Jea48) is the expert when it comes to electrician-type matters, and hopefully he’ll chime in. But FWIW I agree with all of the comments by Dill. I doubt that adding a sub-panel would provide any benefit, and as Dill indicated inserting additional contacts into the path won’t be helpful.

Unless, that is, the sub-panel is something like those made by Equi=Tech which incorporate a high quality transformer and would provide balanced power to the system. However their models cost in the vicinity of $10K or more, and weigh upwards of 300 pounds.

Good luck. Regards,
-- Al