McIntosh Autoformers and Speaker Impedance Dips (KEF Reference 3’s)

Hi, everyone -

I have a new pair of KEF Reference 3’s, and I’m currently trying a McIntosh MA9000 with them. I’ve sampled each of the 8, 4, and 2 ohm taps and decided the 4 ohm connection was the best option with the Ref 3’s. Still... So far, I’m underwhelmed. When I reconnect the Ref 3’s to my Anthem AVM 60 and MCA 525, instruments sound a bit more precise and delineated. My bigger concern is that the McIntosh seems slow and shallow in comparison.

I’m beginning to suspect that some of the difference I’m hearing and initially missing is a bit of brightness in the Anthem that I may have grown used to. Not sure yet. But I don’t think that accounts for the lack of impact/slam from the MA9000. It just doesn’t feel as dynamic. And it’s twice the price of the Anthem pair.

I’ve been reading up on autoformers, which McIntosh (uncommonly?) uses in their SS amps. The KEF’s have a nominal impedance of 8 ohms with a 3.2 ohm minimum at some frequencies. That sounds to me like a fairly dramatic dip, and I’m wondering if the autoformer, which creates separate 8, 4, and 2 ohm taps, is not a good technological match for the KEF’s (as opposed to an amp with one set of taps for the covered impedance range).

Then again, I’ve read up on the changes made to the newer McIntosh MC462, and a lot of focus is directed toward the “66% increase in dynamic headroom” over the previous model MC452 (the 452 obviously itself is a step up from the MA9000, so the 462 should theoretically be a dramatic improvement). So I’m contemplating the C2700 and MC462.

But again... If the autoformer pairing with the KEF impedance dips is problematic, I need to be looking at other options. What do you all think? Are McIntosh amps with autoformers a bad option with speakers that present dramatic impedance fluctuations?

Thanks for any input!

Rob