Here are some gain, impedance and other stats. For those who know about these things, perhaps they help answer the question. Gain looks approximately similar across the board, but input impedance looks different, although I can't interpret the information.

Please let me know what you think.

1. 2250 Amp (which I am using now and which requires me to jack up the volume dial on my preamp):

Gain

Unbalanced 28.3dB

Balanced 22.3dB [NOTE -- I use unbalanced]

Input Impedance

Unbalanced 7K8ohms

Balanced 7K8ohms

Input Level for Clipping

Unbalanced 1.2V rms

Balanced 2.4V rms

Output Power

230W rms into 4 ohms

115W rms into 8 ohms

Maximum Input Power

1000W

Typical Operating Input Power

44W

2. LK 140

Gain

x27 (28.6dB)

Input impedance

10Kohm

Input signal for maximum output

870mV rms

Maximum input power

570W

3. LK 85

Gain

x27 (28.6dB)

Input impedance

10Kohm

Input signal for maximum output

685mV rms

Maximum input power

350W

Please let me know what you think.

1. 2250 Amp (which I am using now and which requires me to jack up the volume dial on my preamp):

Gain

Unbalanced 28.3dB

Balanced 22.3dB [NOTE -- I use unbalanced]

Input Impedance

Unbalanced 7K8ohms

Balanced 7K8ohms

Input Level for Clipping

Unbalanced 1.2V rms

Balanced 2.4V rms

Output Power

230W rms into 4 ohms

115W rms into 8 ohms

Maximum Input Power

1000W

Typical Operating Input Power

44W

2. LK 140

Gain

x27 (28.6dB)

Input impedance

10Kohm

Input signal for maximum output

870mV rms

Maximum input power

570W

3. LK 85

Gain

x27 (28.6dB)

Input impedance

10Kohm

Input signal for maximum output

685mV rms

Maximum input power

350W