Pass Labs preamp with Krell Evo amp. Anyone..??

The specs for the two models do indicate that they differ signficantly. Note that the 402 burns a LOT more power, even in standby, indicating that it's biased more heavily into class A.

On the other hand, the 302's slew rate is faster, and it has a higher damping factor.

So it does make sense that they should sound different.

Also note that at $0.10/kWH, the 302 costs $130 per year in standby, while the 402 costs $320 per year. Not much money compared to the amps themselves though :)

302
Power consumption
Standby: 150 W
Idle: 320 W
Maximum: 3400 W
Slew rate
120 V/µs
Damping Factor (referred to 8 ohms)
>200 at 20 Hz, referred to 8 Ω
>150, 20 Hz to 20 kHz, referred to 8 Ω

402
Power consumption
Standby: 370 W
Idle: 570 W
Maximum: 3800 W
Slew rate
100 V/µs
Damping Factor (referred to 8 ohms)
>145 at 20 Hz, referred to 8 Ω
>125, 20 Hz to 20 kHz, referred to 8 Ω

Turns out the 402's standby and idle power consumption was overstated due to a typo. Krell has updated their site:

402
Power consumption
Standby: 260 W
Idle: 390 W
Maximum: 3800 W
Slew rate
100 V/µs
Damping Factor (referred to 8 ohms)
>145 at 20 Hz, referred to 8 Ω
>125, 20 Hz to 20 kHz, referred to 8 Ω