Hi Russ,

The only speakers I've heard of issues with updating their firmware are the DSP3100's.

I've updated plenty of DSP6000s with v4.x firmware straight up to the latest version without a single incident.
Provided your DSPs are 24/96 versions, then the firmware is software flashable, the 18bit boards use an EPROM chip that needs to be physically changed.

Just make sure you have the correct serial cable, Meridian Flash software, and firmware and you're all set.

I think your dealer must be either confused or scaremongering!

Good luck,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5k.2C, DSP33, F80
Spare: MCD, 100 Series, 200 Series, 500 Series, C15s.