The useful purpose of a custom input stage on most Icepower amps is to raise the input impedance (10K to start with on older versions at least) to enable good performance with higher output impedance tube pre-amplifiers. Its a performance/integration enhancement not just there for "coloration". If pre-amp is lower output impedance SS there is no benefit at least on paper.
Benefits of improved power supply in any amplifier should be obvious.
Benefits of improved power supply in any amplifier should be obvious.