A decently designed supply, either linear or switch mode, should never make any mechanical noise. In a linear supply, that's indicative either of some mechanical fault (transformer laminations separating or transformer incorrectly mounted), or it is due to the transformer saturating. This may be the result of excessive DC offset on the mains, or simply the transformer being poorly specced. If the former, then that's an issue that will potentially adversely affect other equipment, but it's easily addressed.
I personally prefer linear, but that's because I build them and have relevant sim software (and a lot more expereince of them). Virtually all my equipment is valves as well, and high voltages are more easily accomplished with linear supplies. I do have an old laboratory 12 volt SMPS that I've used for some things, but there's not really any advantage for me, as it's the size of two house bricks.
The mains supply to my cottage will not win awards and I'm convinced there is DC offset. I used to have Naim kit, but the buzz ruined my enjoyment of the music. I made numerous attempts to address this with dedicated mains, DC blockers and so on, but to no avail. I did try non-Naim amps, but it was on with the buzzing; although none buzzed quite as loud. My Naim also suffered from radio break through, which was another incentive to move on.
The answer for me was to go for kit that used SMPSs. No more buzz and to my ears music reproduction improved.
To be fair I have heard some fine systems built around Naim kit and the buzz was minimal (hardly audible if at all) and I once got to listen to a system in a neighbour's cottage built around Conrad-Johnson amplification, which didn't buzz at all and was quite superb. I would have thought the neighbour's mains would be no better than mine so perhaps CJ have it cracked.
I'm sure your amplifiers sound superb and had I had one of your designs then I might have avoided the kit changes. My goal is to sit back and listen to the music. I'm happy with my current setup as both Chord and Linn seem to work well for me (though I'm glad I'm not buying anything now after seeing their price increases).
I have heard demonstrations of boutique audiophile switches and music servers and network cables, but heard no improvements. I wonder if those suggesting there are improvements (or in some cases proclaiming it as fact) have listened to a network with fully qualified cabling and HP switches with the edge switches driven by Power over Ethernet. I do not claim it sounds better, but for me it is as good as it gets (Cisco, Juniper and other switches would work well too).