Thieliste, No, what’s important is that the amp is capable of delivering the power into the actual impedance load. Note how some amps will blow a fuse with just 1 channel running into such a load, never mind both. Or that sometimes an amp is not even tested into 2 Ohms. Guess why?
Some so called Class A amps decrease the percentage of Class A bias output as the power increases into lower impedances.
With most typical speakers (like the 3.7’s), as the impedance drops so does the sensitivity.
400 Watts into 2 Ohms might seem excessive, but consider that is comperable to 100 Watts into 8 Ohms.
I’m not suggesting that you need a 600 Watt high current amp (advantages aside); your room and desired listening levels will determine that. Just that Thiel’s minimum recommendation calls for close to 400 Watts into close to 2 (!) Ohms. I recommend getting an amp that is not regularly on the verge of it’s limits.
Given that an amp is capable delivering it’s power into a given impedance, it depends on the circumstances as to whether or not more power or more refinement is better. A more refined amp regularly driven into clipping would sound less
desirable and potentially be more likely to damage a speaker than a smooth running less refined higher powered amp. While unto itself Class A can be desirable, it’s just one consideration amongst many in determining the the overall quality of an amp. I’ve heard Class AB amps that sounded preferable to some Class A amps regardless of power output. And visa versa..