http://www2.rdrop.com/users/twest/audio/index.html
As discussed extensively below, the solution for the first two issues an active vertical biamp combined with low impedance cabling. The second two issues are addressed by balanced interconnects and reducing power amplifier gain—one of the odd things about audio is preamplifiers don't actually amplify. They attenuate. Line level out of a CD player is a few hundred millivolts RMS, but typical voltages at the drivers are maybe 100 mV RMS. In order to achieve a couple hundred watts of output power, power amplifiers have voltage gains around 30 dB. The preamp therefore ends up attenuating by 50 dB, meaning RMS voltages in preamp output stages, active crossovers, and power amp input stages are hundreds of microvolts. This exacerbates pickup of ground bounce or supply ripple coupling into power amp input stages and degrades op amp performance. The fix is simple; turn the power amp down and the preamp up. In an active biamp, unity power amplifier gain generally provides sufficient SPL and increases the SNR of most parts of the signal path by 30 dB. A secondary benefit is op amps behind the preamplifer's volume control operate closer to their line level sweet spot. With current generation op amps such as the LME49740 the benefit is small compared to speaker and power stage limitations, but there can be noticeable improvement in the volume control IC or with older op amps.