tomthiel, I humbly(!) submit that I'm a bit disappointed that you would choose the Benchmark as a reference amp. While probably a very fine amplifier in other circumstances, it seems less than ideal for the task at hand.
https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-specifications
This rated 100 Watt (which is the minimum power recommendation for many Thiel loudspeakers) amp with it's balanced only inputs is not compatible with Thiel 3.5's, is not spec'd to double down into 4 Ohms, is only spec'd to 3 Ohms where it's only putting out 240 Watts and not to the sub 3 Ohm levels of some Thiel loudspeakers.
If one had already purchased Thiel maximum power recommended amps capable of 2400 Watts into 2 Ohms (wall power permitting), I think they might think twice before upgrading to "hot rodded" versions that were not tested the maximum output, never mind only tested into 1/10th of that.
After hearing years of complaints from those that have not done their due diligence and used inappropriate amplification and then gone on to disparage the Thiel loudspeakers, I would imagine that setting such an example might be fraught with potential backlash.
Most of the Thiel loudspeakers under consideration here are far from new. I submit that amplifiers with much better and more appropriate capabilities from their own era can be found at comparable prices.