Electrical fields

You should be good to go at 2', particularly if the cabinent of your breaker box is made from steel. If you want more shielding, any steel that a magnet sticks to will work.
With industrial equipment, you sometimes see conductors or busswork carrying hundreds or thousands of amps located within your 2' of computer equipment and/or very sensitive low level input signal terminations. Stay away from running stereo cables in parallel with current carrying conductors & you should be fine.

The impact of electrical field is halved every time the space or distance is doubled. I would not get anywhere near 2' from the box. I'm about 25' from the box and that's plenty close enough!

Get as far away as is reasonably possible.

I agree with Jeff.

Hmm, it seems there are varying opinions. This should be a simple matter for a someone with a EE or physics degree. Neither of which I have. I guess once test is to move the stuff and then listen!

I have a couple EE degrees and still agree with Jeff.