Doesn't the AHB2 accomplish this?
Not really, because I think beagleman 's point is not (or not just..) about the double down capability but also what he said in his last sentence "
An amp great at low impedances, by its very design will lose performance at higher or normal impedance"
The AHB2 can almost double down into 4 ohms, but definitely not 2 Ohms.
As beagleman predicted, it "performance at higher impedance....", in this case, only 100 W into 8 Ohms, that is clearly not due to current capability but most likely voltage capability.
Take a look of the voltage requirements for the varying load impedance, based on the same current capability (Power = V^2/R, or I^2*R):
Voltage = square root of P*R,
I = square root of P/R
For 190 W, 4 ohms, Voltage required = square root 190*4 = 27.57 V, and Current = square root of 190/R = 6.892 A
Since it is capable of 6.892 A, the theoretical power output capability should be:
Power (W) = I^2*R = 380 W into 8 ohms, but the amp is only rated 100 W into 8 ohms. This amp may not perform as well when driving certain so called 8 ohm nominal, but with high peak impedance speakers than those nominal 4 ohms with low dip ones, when operating at or near its power output limit.
In short, if an amp is designed to double down (that is almost double down), it will have trouble to "double up". Hence a compromise, that need to be done for the targeted type of load for the targeted applications.
That's the nice thing about objective measurements, I most likely don't agree with
@beagleman based on his/my subjective views/preference, but on the objective side, I have no choice but to agree with him on things he posted that are based on engineering principles.
Based on Benchmark's website information for the AHB2's power output for various load impedance:
CONTINUOUS AVERAGE OUTPUT POWER
< 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz
- 100 Watts per channel into 8 Ohms, both channels driven
- 130 Watts per channel into 6 Ohms, both channels driven
- 190 Watts per channel into 4 Ohms, both channels driven